uart_dm: Add dsb() barrier.
uart_dm: Add dsb() barrier.

Add dsb instructions to make sure correct sequence of uart intialization.

Change-Id: I5a9bcc924c7df7297e3ea06c3b050ff1d01bf311

jbott/lk_gee,idor/dk50-bootable_bootloader_lk,mozilla-b2g/kernel_lk,thornbirdblue/codeaurora_lk,jsr-d9/android_kernel_lk,M1cha/android_bootable_bootloader_lk,RonGokhale/android_lk_bootloader,lg-devs/g2-bootloader,lg-devs/g2-bootloader,zhuotong/mi2_lk_NoEmmc,jbott/lk_gee,t2m-foxfone/android_kernel_lk,M1cha/mi2_lk,mozilla-b2g/fairphone2_kernel_lk,MiCode/mi2_lk,efidroid/lk,MiCode/mi2_lk,efidroid/lk,t2m-foxfone/android_kernel_lk,Redmi-dev/android_bootable_lk,hanjae/lumiab0,idor/dk50-bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,thornbirdblue/codeaurora_lk,Blefish/android_bootable_bootloader_lk,M1cha/mi2_lk,oubeichen/lk-v500,utilite2/lk,beidl/lk_umia,thornbirdblue/codeaurora_lk,hanjae/lumiab0,jsr-d9/android_kernel_lk,Foxda-Tech/argo8-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,CanarySolutions/little-kernel,t2m-foxfone/android_kernel_lk,pichina/lk,Blefish/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,lg-devs/g2-bootloader,chirayudesai/android_bootable_bootloader_lk,M1cha/android_bootable_bootloader_lk,chirayudesai/android_bootable_bootloader_lk,RonGokhale/android_lk_bootloader,RonGokhale/android_lk_bootloader,lg-devs/g2-bootloader,utilite2/lk,DooMLoRD/android_bootable_bootloader_lk,mozilla-b2g/kernel_lk,t2m-foxfone/android_kernel_lk,MiCode/mi2_lk,thornbirdblue/codeaurora_lk,CanarySolutions/little-kernel,mozilla-b2g/fairphone2_kernel_lk,jsr-d10/android_bootable_bootloader_lk,my4ndr0id/android_bootable_bootloader_lk,M1cha/lktris,Foxda-Tech/polaris-bootable-bootloader-lk,oubeichen/lk-v500,detule/lk-g2-spr,zhuotong/mi2_lk_NoEmmc,jbott/lk_gee,Foxda-Tech/argo8-bootable-bootloader-lk,my4ndr0id/android_bootable_bootloader_lk,M1cha/lktris,RonGokhale/android_lk_bootloader,t2m-foxfone/kernel_lk,jsr-d9/android_kernel_lk,zhuotong/mi2_lk_NoEmmc,utilite2/lk,RonGokhale/android_lk_bootloader,utilite2/lk,M1cha/lktris,my4ndr0id/android_bootable_bootloader_lk,chirayudesai/android_bootable_bootloader_lk,mozilla-b2g/kernel_lk,Foxda-Tech/argo8-bootable-bootloader-lk,M1cha/lktris,t2m-foxfone/kernel_lk,zhuotong/mi2_lk_NoEmmc,hanjae/lumiab0,pichina/lk,oubeichen/lk-v500,hanjae/lumiab0,M1cha/lktris,jsr-d10/android_bootable_bootloader_lk,Foxda-Tech/argo8-bootable-bootloader-lk,efidroid/lk,DooMLoRD/android_bootable_bootloader_lk,jbott/lk_gee,jsr-d10/android_bootable_bootloader_lk,CanarySolutions/little-kernel,pichina/lk,jsr-d9/android_kernel_lk,oubeichen/lk-v500,pichina/lk,Foxda-Tech/polaris-bootable-bootloader-lk,CanarySolutions/little-kernel,Blefish/android_bootable_bootloader_lk,DooMLoRD/android_bootable_bootloader_lk,jbott/lk_gee,MiCode/mi2_lk,beidl/lk_umia,beidl/lk_umia,t2m-foxfone/kernel_lk,jsr-d10/android_bootable_bootloader_lk,my4ndr0id/android_bootable_bootloader_lk,lg-devs/g2-bootloader,thornbirdblue/codeaurora_lk,Redmi-dev/android_bootable_lk,pichina/lk,efidroid/lk,M1cha/android_bootable_bootloader_lk,Foxda-Tech/argo8-bootable-bootloader-lk,chirayudesai/android_bootable_bootloader_lk,Redmi-dev/android_bootable_lk,M1cha/mi2_lk,t2m-foxfone/android_kernel_lk,CanarySolutions/little-kernel,hanjae/lumiab0,Redmi-dev/android_bootable_lk,utilite2/lk,mozilla-b2g/kernel_lk,chirayudesai/android_bootable_bootloader_lk,Foxda-Tech/polaris-bootable-bootloader-lk,M1cha/android_bootable_bootloader_lk,zhuotong/mi2_lk_NoEmmc,mozilla-b2g/kernel_lk,detule/lk-g2-spr,MiCode/mi2_lk,efidroid/lk,Blefish/android_bootable_bootloader_lk,my4ndr0id/android_bootable_bootloader_lk,Foxda-Tech/polaris-bootable-bootloader-lk,Redmi-dev/android_bootable_lk,DooMLoRD/android_bootable_bootloader_lk,M1cha/mi2_lk,t2m-foxfone/kernel_lk,mozilla-b2g/fairphone2_kernel_lk,idor/dk50-bootable_bootloader_lk,idor/dk50-bootable_bootloader_lk,beidl/lk_umia,oubeichen/lk-v500,M1cha/android_bootable_bootloader_lk,detule/lk-g2-spr,t2m-foxfone/kernel_lk,detule/lk-g2-spr,M1cha/mi2_lk,M1cha/android_bootable_bootloader_lk,jsr-d9/android_kernel_lk,beidl/lk_umia,DooMLoRD/android_bootable_bootloader_lk,Blefish/android_bootable_bootloader_lk,detule/lk-g2-spr,mozilla-b2g/fairphone2_kernel_lk,idor/dk50-bootable_bootloader_lk