platform: msm_shared: fix for fastboot erase aboot.
platform: msm_shared: fix for fastboot erase aboot.

fastboot erase command never returns success if erase block
start and end address are same.In unaligned block head case,
check the second block whether to use the emmc erase function
or write zero's to emmc.

CRs-Fixed: 718893.
Change-Id: I3c0a587838489d43ca139f436e176b1fbd52d4d1

CanarySolutions/little-kernel,efidroid/lk,CanarySolutions/little-kernel,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,efidroid/lk,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,efidroid/lk,Foxda-Tech/polaris-bootable-bootloader-lk,Foxda-Tech/polaris-bootable-bootloader-lk,efidroid/lk,Foxda-Tech/polaris-bootable-bootloader-lk,CanarySolutions/little-kernel,efidroid/lk