drm/i915/tgl: Report valid VDBoxes with SFC capability

In Gen11, only even numbered "logical" VDBoxes are hooked up to a SFC
(Scaler & Format Converter) unit. This is not the case in Tigerlake,
where each VDBox can access a SFC.

We will use this information to decide when the SFC units need to be reset
and also pass it to the GuC.

Bspec: 48077
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190731004902.34672-5-daniele.ceraolospurio@intel.com