drm: mali-dp: Fix destination size handling when rotating

The destination rectangle provided by userspace in the CRTC_X/Y/W/H
properties is already expressed as the dimensions after rotation.
This means we shouldn't swap the width and height ourselves when a
90/270 degree rotation is requested, so remove the code doing the swap.

Fixes: ad49f860 ("drm/arm: Add support for Mali Display Processors")

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>