[media] videodev2.h: add __user to v4l2_ext_control pointers

These are not copied to kernel space by video_usercopy, so mark them
as __user.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

include/uapi/linux/videodev2.h

@@ -1285,11 +1285,11 @@ struct v4l2_ext_control {
 	union {
 		__s32 value;
 		__s64 value64;
-		char *string;
-		__u8 *p_u8;
-		__u16 *p_u16;
-		__u32 *p_u32;
-		void *ptr;
+		char __user *string;
+		__u8 __user *p_u8;
+		__u16 __user *p_u16;
+		__u32 __user *p_u32;
+		void __user *ptr;
 	};
 } __attribute__ ((packed));