drm/i915: Check SFC fusing before recording/dumping SFC_DONE

On Xe_HP and beyond the SFC unit may be fused off, even if the
corresponding media engines are present.  Check the SFC-specific fusing
before trying to dump the SFC_DONE instances.

Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210917161203.812251-3-matthew.d.roper@intel.com