FBC is no longer limited by pipe: add the defines for pipes B and C that
will be used by platforms supporting FBC on such pipes.

Bspec: 68881, 68904
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919192128.2045154-3-lucas.demarchi@intel.com