Move the sprite colorkey ioctl handler to its own file
so that intel_sprite.c becomes all about the low level
details of pre-skl sprite planes.

And drop a bunch of unnecessary includes while at it.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230314130255.23273-10-ville.syrjala@linux.intel.comReviewed-by: Jouni Högander <jouni.hogander@intel.com>