drm/i915: Set has_fbc=true for all SNB+, except VLV

At least since SNB (perhaps even earlier) even the desktop parts
should have FBC.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>