gpu: Add export.h as required to drivers/gpu files.

They need this to get all the EXPORT_SYMBOL variants and THIS_MODULE

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

drivers/gpu/drm/i915/intel_dp.c

@@ -27,6 +27,7 @@
 
 #include <linux/i2c.h>
 #include <linux/slab.h>
+#include <linux/export.h>
 #include "drmP.h"
 #include "drm.h"
 #include "drm_crtc.h"