lib: arm_ffa: Continue FFA init if MEM_RETRIEVE_REQ is not supported am: 49a2a37f29

Original change: https://android-review.googlesource.com/c/trusty/lk/trusty/+/3488312

Change-Id: I84884b3947734028eabd74f105734f570b965406
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>