msm_fb: display: add spinlock to protect dma status.

During dma transfer to interface host the status of the dma
needs to be protected in the smp environment.

Change-Id: I02b4f046de7f693bb098343b7345c4aa6ca395bd
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>
Signed-off-by: Ronny Schmatzler <schmatzler@googlemail.com>
Fix-up