We have a src and dect rectangle, use it instead of relying on
the core drm properties.

Because the core by default clips the src/dst properties, after
the drm_atomic_helper_check_plane_state() we manually set the
unclipped src/dst rectangles. We still need the call for
visibility checks, but this way we are able to use the src/dst
rects in the check/commit code.

This removes the special case in the watermark code for cursor w/h.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004113514.17064-5-maarten.lankhorst@linux.intel.comReviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[mlankhorst: Clarify commit message to state we use unclipped src/dst