dsp: Add cmd locks to fix synchronization issues

Add mutex locks in q6core_send_get_avcs_fwk_ver_cmd()
and q6core_map_mdf_shared_memory() functions to fix
command-response synchronization issues in race conditions.

Change-Id: Ibdf6788b51965bd37245c611683102c600ca8eb4
Signed-off-by: Harshal Ahire <hahire@codeaurora.org>