msm: lmh_lite: Enable interrupt inside critical section

Interrupt enable code is outside the critical section and
this can lead to race condition between multiple threads.
This race condition can result in enabling the interrupt,
which is disabled by the interrupt service routine. This
can lead to interrupt storm.

To avoid this, the interrupt enable is done inside critical
section to avoid any race condition.

CRs-Fixed: 850290
Change-Id: Ifeea212601e39b554740d88da0c662e4a9be0d87
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>