On BMG-G21 we need to disable fbc due to complications around the WA.

v2:
 - Try to handle with i915_drv.h and compat layer. (Rodrigo)
v3:
 - For simplicity retreat back to the original design for now.
 - Drop the extra \ from the Makefile (Jani)
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Vinod Govindapillai <vinod.govindapillai@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240703124338.208220-4-matthew.auld@intel.com