Revert "SPM: Remove tfm_spm_get_msg_buffer_from_conn_handle"

This reverts commit ae8965e14264973890a9a03c061264c750703d06.

Revert because it was merged by accident without enough review.

Change-Id: I454513b4a157312b658473a6c79ee9ef410245ce
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
3 files changed