disp: msm: sde: allocate virtually contiguous memory

This change uses kvzalloc to allocate memory for lutdma buffers.
This is needed since kernel cannot guarantee that physically
contiguous allocations greater than 32 KB will succeed.

Change-Id: I91c12bbd612408692ba8e4a3cd9ac1ce308eda64
Signed-off-by: Anjaneya Prasad Musunuri <aprasad@codeaurora.org>