msm: smem: add smem_get_version() API

The smem_get_version() API is used to read the smem user version number
from the SMEM_VERSION_INFO table.

Change-Id: I4e5ba542716d2137bab41c2100b2553fd72b722a
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>