drm/mali-dp: Align pitch size to be multiple of bus burst read size.

Mali DP hardware needs pitch line sizes aligned to the bus burst
size for reads, so take that into consideration when allocating dumb
buffers. If the layer is rotated then the stride size requirement is
even larger for some hardware versions, so allocate for the worst case
scenario. Update the ->dumb_create() hook to a driver specific function
that sets the correct pitch size.

Reported-by: Ayan Halder <ayan.halder@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>