drm/i915: remove unnecessary check for crtc->primary->fb

We already check if the CRTC is visible, and it shouldn't be possible
to have a visible CRTC without an FB.

This was noticed by both Chris and Ville on different ocasions.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446664257-32012-4-git-send-email-paulo.r.zanoni@intel.comSigned-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_fbc.c

@@ -503,7 +503,7 @@ static struct drm_crtc *intel_fbc_find_crtc(struct drm_i915_private *dev_priv)
 			break;
 	}
 
-	if (!crtc || crtc->primary->fb == NULL)
+	if (!crtc)
 		return NULL;
 
 	return crtc;