target: apq8084: Implement target specific ssd api
target: apq8084: Implement target specific ssd api

Implement target specific ssd api to load keystore when entering
fastboot to enable flashing encrypted images.

CRs-Fixed: 586343
Change-Id: Ie81576948ccfe6921b48ef8310e91a5027571304

Foxda-Tech/argo8-bootable-bootloader-lk,M1cha/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,Foxda-Tech/polaris-bootable-bootloader-lk,CanarySolutions/little-kernel,M1cha/lktris,Foxda-Tech/argo8-bootable-bootloader-lk,efidroid/lk,M1cha/android_bootable_bootloader_lk,M1cha/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,efidroid/lk,jsr-d10/android_bootable_bootloader_lk,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,CanarySolutions/little-kernel,M1cha/android_bootable_bootloader_lk,M1cha/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,efidroid/lk,efidroid/lk,Foxda-Tech/polaris-bootable-bootloader-lk,jsr-d10/android_bootable_bootloader_lk,efidroid/lk,Foxda-Tech/polaris-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,M1cha/lktris,CanarySolutions/little-kernel,M1cha/lktris,M1cha/lktris,M1cha/lktris,Foxda-Tech/argo8-bootable-bootloader-lk,Foxda-Tech/argo8-bootable-bootloader-lk,Foxda-Tech/argo8-bootable-bootloader-lk,CanarySolutions/little-kernel,M1cha/android_bootable_bootloader_lk