drm: Use horizontal and vertical chroma subsampling factor while calculating offsets...

drm: Use horizontal and vertical chroma subsampling factor while calculating offsets in the physical address of framebuffer

For multi-planar formats, while calculating offsets in planes with index greater than 0
(ie second plane, third plane, etc), one needs to divide (src_x * cpp) with horizontal
chroma subsampling factor and (src_y * pitch) with vertical chroma subsampling factor.

The reason being that the planes contain subsampled (ie reduced) data (by a factor of 2) and thus
while calculating the byte position coresponding to the x and y co-ordinates, one needs to
divide it with the sampling factor.

Signed-off-by: Ayan Kumar halder <ayan.halder@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.kernel.org/patch/10569263/