drm: Add drm_rect rotation functions

Add some helper functions to move drm_rects between different rotated
coordinate spaces. One function does the forward transform and
another does the inverse.

Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Acked-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_rect.h b/include/drm/drm_rect.h
index d128629..26bb55e 100644
--- a/include/drm/drm_rect.h
+++ b/include/drm/drm_rect.h
@@ -163,5 +163,11 @@
 				 struct drm_rect *dst,
 				 int min_vscale, int max_vscale);
 void drm_rect_debug_print(const struct drm_rect *r, bool fixed_point);
+void drm_rect_rotate(struct drm_rect *r,
+		     int width, int height,
+		     unsigned int rotation);
+void drm_rect_rotate_inv(struct drm_rect *r,
+			 int width, int height,
+			 unsigned int rotation);
 
 #endif