msm: ais: reqmgr: reader writer locks to avoid memory faults

Shared memory is initialized by CRM and used by
other drivers; with CRM not active other drivers
would fail to access the shared memory if
memory manager is deinit. Reader Writer locks can
prevent the open/close/ioctl calls from other drivers
if CRM open/close is already being processed.
Issue observed with the below sequence if drivers
are opened from UMD directly without this change.
CRM Open successful,ICP open successful,
CRM close in progress, ICP open successful,
mem mgr deinit and CRM close successful,
ICP tries to access HFI memory and results in crash.
This change helps to serialze the calls and prevents
issue.

Change-Id: I37c55652835f66ee30af383e80e96ff9f117be35
Signed-off-by: E V Ravi <quic_evenka@quicinc.com>