drm/i915: Start tracking PIPESRC as a drm_rect

Instead of just having the pipe_src_{w,h} let's use a full
drm_rect for it. This will be particularly useful to astract
away some bigjoiner details.

v2: No hweight() stuff yet

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220223131315.18016-11-ville.syrjala@linux.intel.com


Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>