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/video/v4l2-ctrls.c b/drivers/media/video/v4l2-ctrls.c
index 06b6014..f7824a0 100644
--- a/drivers/media/video/v4l2-ctrls.c
+++ b/drivers/media/video/v4l2-ctrls.c
@@ -20,6 +20,7 @@
 
 #include <linux/ctype.h>
 #include <linux/slab.h>
+#include <linux/export.h>
 #include <media/v4l2-ioctl.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-ctrls.h>