drm/i915: free intel_fb

We need to free the allocated intel_fb in the error path, not
intel_fb->base. Otherwise we risk calling kfree with a non-kmalloc'd
address, which is bound to give us grief at some point.
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471964444-24460-1-git-send-email-matthew.auld@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -9777,7 +9777,7 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
 	return;
 
 error:
-	kfree(fb);
+	kfree(intel_fb);
 }
 
 static void ironlake_get_pfit_config(struct intel_crtc *crtc,