drm/i915/tgl: Assume future platforms will inherit TGL's SFC capability

drm/i915/tgl: Assume future platforms will inherit TGL's SFC capability

Our usual i915 convention is to assume that future platforms will follow
the same behavior as the latest platform of today.  The VDBOX/SFC
capabilities described here don't seem like something that should be
specific to TGL, so let's future-proof by making the test apply to all
gen12+ platforms.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191224231521.3430660-1-matthew.d.roper@intel.com
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>