drm/i915: Enable RGB565 90/270 plane rotation for gen11 onwards.

From gen11 onwards RGB565 90/270 plane rotation is supported on hardware.

IGT: https://patchwork.freedesktop.org/series/48756/
Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[mlankhorst: Rebase on top of current dinq (self), fix grammar (Ville).]
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1535373473-3594-3-git-send-email-juhapekka.heikkila@gmail.com