msm: mdss: Fix potential race condition in rotator

There might be a possible race condition in rotator, where two
threads can free same perf structures. Adding proper locking
to avoid such race conditions.

Change-Id: I4976da6f176df24da2ec86c4c1f176cc43aba05b
Signed-off-by: Krishna Chaitanya Devarakonda <kdevarak@codeaurora.org>
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>