drm/sti: Fix compilation failure for drm_framebuffer.pixel_format

drivers/gpu/drm/sti/sti_plane.c:76:33: error: ‘struct drm_framebuffer’
has no member named ‘pixel_format’; did you mean ‘format’?

I didn't look to hard at the casting to a char * and just did a
mechanical transformation of s/pixel_format/format->format/ as given in
commit 438b74a5497c ("drm: Nuke fb->pixel_format").

Fixes: 438b74a5497c ("drm: Nuke fb->pixel_format")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Acked-by: Vincent Abriou <vincent.abriou@st.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/sti/sti_plane.c

@@ -73,7 +73,7 @@ void sti_plane_update_fps(struct sti_plane *plane,
 			 plane->drm_plane.name,
 			 plane->drm_plane.fb->width,
 			 plane->drm_plane.fb->height,
-			 (char *)&plane->drm_plane.fb->pixel_format,
+			 (char *)&plane->drm_plane.fb->format->format,
 			 fpks / 1000, fpks % 1000,
 			 sti_plane_to_str(plane));
 	}