drm/arcpgu: Add local 'fb' variables

Add a local 'fb' variable to a few places to get rid of the
'crtc->primary->fb' stuff. Looks neater and helps me with my ppor
coccinelle skills later.

Cc: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479498793-31021-9-git-send-email-ville.syrjala@linux.intel.comAcked-by: Alexey Brodkin <abrodkin@synopsys.com>

drivers/gpu/drm/arc/arcpgu_crtc.c

@@ -35,7 +35,8 @@ static struct simplefb_format supported_formats[] = {
 static void arc_pgu_set_pxl_fmt(struct drm_crtc *crtc)
 {
 	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
-	uint32_t pixel_format = crtc->primary->state->fb->pixel_format;
+	const struct drm_framebuffer *fb = crtc->primary->state->fb;
+	uint32_t pixel_format = fb->pixel_format;
 	struct simplefb_format *format = NULL;
 	int i;