platform: msm_shared: Decouple save kernel hash

The hash of the kernel is sent to tz. This is only needed
when the image is verified successfully. This change prevents
sending the hash to TZ twice in case of calling the
boot_verify_compare_sha256 function twice

Change-Id: I0dbe72597fbb57164e5a223d689b9d8f26b16ba9
3 files changed