msm:camera:lrme: Fix LRME context Ref Count leak

LRME ref count is not done properly. It will lead to context ref
count leak.

This change prevents ref count leak by checking refcount value before
decrementing the ref count. It is making sure the ref count never goes
below zero.

Change-Id: Ie6927eb7465ec656cdc959a39fbefe79dcc511fa
Signed-off-by: Chandan Kumar Jha <cjha@codeaurora.org>