target: msm8974: Fix platform subtype
target: msm8974: Fix platform subtype

8974 targets have a new platform subtype for msm8974pro
version of chips. Add this new platform subtype & remove
MDM subtype for msm8974 which may never be true.

Change-Id: I80154430ab16591324fb0a4f3fbd633899066eff

mozilla-b2g/kernel_lk,M1cha/lktris,idor/dk50-bootable_bootloader_lk,M1cha/lktris,Foxda-Tech/argo8-bootable-bootloader-lk,t2m-foxfone/android_kernel_lk,efidroid/lk,Foxda-Tech/polaris-bootable-bootloader-lk,jbott/lk_gee,idor/dk50-bootable_bootloader_lk,efidroid/lk,CanarySolutions/little-kernel,detule/lk-g2-spr,mozilla-b2g/fairphone2_kernel_lk,CanarySolutions/little-kernel,Foxda-Tech/argo8-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,mozilla-b2g/kernel_lk,CanarySolutions/little-kernel,mozilla-b2g/kernel_lk,mozilla-b2g/kernel_lk,mozilla-b2g/fairphone2_kernel_lk,lg-devs/g2-bootloader,detule/lk-g2-spr,M1cha/android_bootable_bootloader_lk,t2m-foxfone/android_kernel_lk,t2m-foxfone/kernel_lk,t2m-foxfone/kernel_lk,idor/dk50-bootable_bootloader_lk,Redmi-dev/android_bootable_lk,lg-devs/g2-bootloader,jbott/lk_gee,M1cha/android_bootable_bootloader_lk,CanarySolutions/little-kernel,detule/lk-g2-spr,detule/lk-g2-spr,M1cha/lktris,M1cha/lktris,jbott/lk_gee,Foxda-Tech/argo8-bootable-bootloader-lk,idor/dk50-bootable_bootloader_lk,t2m-foxfone/kernel_lk,detule/lk-g2-spr,mozilla-b2g/fairphone2_kernel_lk,Redmi-dev/android_bootable_lk,M1cha/lktris,CanarySolutions/little-kernel,t2m-foxfone/android_kernel_lk,Foxda-Tech/polaris-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,Redmi-dev/android_bootable_lk,t2m-foxfone/kernel_lk,mozilla-b2g/kernel_lk,Foxda-Tech/argo8-bootable-bootloader-lk,lg-devs/g2-bootloader,efidroid/lk,jsr-d10/android_bootable_bootloader_lk,efidroid/lk,lg-devs/g2-bootloader,M1cha/android_bootable_bootloader_lk,Redmi-dev/android_bootable_lk,t2m-foxfone/android_kernel_lk,Redmi-dev/android_bootable_lk,M1cha/android_bootable_bootloader_lk,jbott/lk_gee,t2m-foxfone/kernel_lk,jsr-d10/android_bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,M1cha/android_bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,jsr-d10/android_bootable_bootloader_lk,idor/dk50-bootable_bootloader_lk,Foxda-Tech/argo8-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,lg-devs/g2-bootloader,t2m-foxfone/android_kernel_lk,jsr-d10/android_bootable_bootloader_lk,M1cha/android_bootable_bootloader_lk,efidroid/lk,jsr-d10/android_bootable_bootloader_lk,jbott/lk_gee