drm/i915/skl: Allow scanning out Y and Yf fbs

drm/i915/skl: Allow scanning out Y and Yf fbs

Skylake is able to scannout those tiling formats. We need to allow them
in the ADDFB ioctl and tell the harware about it.

v2: Rebased for addfb2 interface. (Tvrtko Ursulin)
v3: Rebased for fb modifier changes. (Tvrtko Ursulin)
v4: Don't allow Y tiled fbs just yet. (Tvrtko Ursulin)
v5: Check for stride alignment and max pitch. (Tvrtko Ursulin)
v6: Simplify maximum pitch check. (Ville Syrjälä)
v7: Drop the gen9 check since requirements are no different. (Ville Syrjälä)
v8: Gen2 has different X tiling stride. (Ville Syrjälä)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com> (v7)
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>