platform: msm-shared: Include date in boot security patch

Read the value of boot security patch containing
date information, from the property com.android.
build.boot.security_patch in vbmeta data and send
it to keymaster TA. This new patch value contains
date information as well. If the property is not
defined or keymaster TA is not updated, send the
security patch value read from boot image header
as before.

Change-Id: I46544a1d37d5f08fd819802410e2960da2d326e8