msm: synx: release reference holding the lock

The reference acquired by the synx release function
at the start of the function is decremented outside
the mutex lock.
Also fix index value used while acquiring lock during
table read as row->index variable can be cleaned
by release function.

Change-Id: Id8edda1b90411e3b51d6859762d31f7ec42c530b
Signed-off-by: Sumukh Hallymysore Ravindra <quic_shallymy@quicinc.com>