gpu: add module.h to drivers/gpu files as required.

So that we don't get build failures once the implicit module.h
presence is removed.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/gpu/drm/drm_encoder_slave.c

@@ -24,6 +24,8 @@
  *
  */
 
+#include <linux/module.h>
+
 #include "drm_encoder_slave.h"
 
 /**