msm: synx: Perform idr access with lock

Perform IDR function access by holding on to the lock
which otherwise could lead to synchronization issues
and race conditions.
Additionally check for the id returned and return error
if id allocation failed.

Change-Id: I88be2883b20e3bbd6029d9f2caae6096907e4c09
Signed-off-by: Sumukh Hallymysore Ravindra <shallymy@codeaurora.org>