drm/mali-dp: Rectify the width and height passed to rotmem_required()

The width and height needs to be swapped

Signed-off-by: Ayan Kumar halder <ayan.halder@arm.com>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
[rebased on top of v4.18-rc1]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>