mdss: dsi: pass controller device to DMA APIs

DMA allocation API requires a non-null device
for DMA buffer allocation. This allows for
device specific book-keeping of DMA buffers.
Pass the DSI controller device for such allocation.

Change-Id: I37695bbe7481a2d842fb705a5ef567dbb9049de3
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>