msm: ADSPRPC: Fix to avoid Use after free in fastrpc_init_process

Allow single thread to execute FASTRPC_INIT_CREATE
to avoid UAF scenario.

Change-Id: Id4ba1a406ace04d46482cd8b14c9d9ef5c96c4a1
Acked-by: Nishant Chaubey <chaubey@qti.qualcomm.com>
Signed-off-by: Vamsi Krishna Gattupalli <quic_vgattupa@quicinc.com>