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>
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 2eee8e0..0f9ef9b 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -16,6 +16,7 @@
 #include <linux/kdev_t.h>
 #include <linux/gfp.h>
 #include <linux/err.h>
+#include <linux/export.h>
 
 #include "drm_sysfs.h"
 #include "drm_core.h"