drm/amd/display: Report stream as different on scaling change

When scaling is enabled, our preference is to scale up to the prefered
(native) mode. This means that hardware timings will be the same across
a modeset.

Therefore, also report mode as changed if source or destination
rectangle is different.

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>