msm: kgsl: Do not hold memory spinlock when calling find region function

The function kgsl_sharedmem_find_region holds the memory spinlock
at the beginning of the function so we do not need to hold the lock
before calling the function

Change-Id: I20ee32e0ed6aee6ed61cdd4fb7a9cc08a876fc84
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>