A couple of PLANE_WM bits were still using the hand
rolled (1<<N) form. Replace with REG_BIT().

v2: Rebase
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240513165945.15285-1-ville.syrjala@linux.intel.com