msm: cpr: Replace mutex with spinlock in atomic context

The CPR suspend is called in an atomic context which leads
to failure if mutex is used before disabling CPR. Replace
with spinlock to fix it.

Change-Id: Ifb23e3988b79ebb0810af88b45d88b778c7c9015
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>