drivers/media: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required

These two macros were in module.h but now module.h is no longer
sprayed across every source file imaginable, so the users need
to expicitly call out their use of them.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index 16b70b4..6edc9ba 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -23,6 +23,7 @@
 #include <linux/types.h>
 #include <linux/ioctl.h>
 #include <linux/media.h>
+#include <linux/export.h>
 
 #include <media/media-device.h>
 #include <media/media-devnode.h>