disp: msm: sde: avoid using spinlock for register log

Add support to use atomic variable instead of
spinlock for register logs during register
write. In the current architecture, register
writes are serialised and happen in commit
context.

Change-Id: I2a0b8ae404c94807ef06141867ee427909498ebf
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>