platform: msm_shared: Fix value passed to data length for unmap command
platform: msm_shared: Fix value passed to data length for unmap command

Currently the data length field of unmap is assigned the length
considering index starting from 1 instead of 0. Fix this to ensure
the index counting starts from 0

Change-Id: Id00208284479124bc730a7627ffd04f28ffd8fad

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