drm/tests: Set also mock plane src_x, src_y, src_w and src_h

We need to set also src_x, src_y, src_w and src_h for the mock plane.
After fix for drm_atomic_helper_damage_iter_init we are using these
when iterating damage_clips.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220823112920.352563-5-jouni.hogander@intel.com


Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Tested-by: Maíra Canal <mairacanal@riseup.net>