FBC is supported with RGB32 8:8:8:8 with or without alpha

Bspec: 68904, 69560
Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230922133003.150578-3-vinod.govindapillai@intel.com