Use REG_BIT() & co. to polish the ivb+ sprite plane registers.

v2: deal with gvt
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211201152552.7821-9-ville.syrjala@linux.intel.comReviewed-by: José Roberto de Souza <jose.souza@intel.com>