V4L/DVB (4108): Fixes some userspace dependencies at V4L2 public api header

Make life easier for distro guys, by removing the need of including
at the userspace header.
Also, linux/compiler.h is not needed at userspace.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

include/linux/videodev2.h

@@ -15,10 +15,12 @@
 #ifndef __LINUX_VIDEODEV2_H
 #define __LINUX_VIDEODEV2_H
 #ifdef __KERNEL__
-#include <linux/time.h> /* need struct timeval */
+#include <linux/time.h>     /* need struct timeval */
+#include <linux/compiler.h> /* need __user */
+#else
+#define __user
 #endif
 #include <linux/types.h>
-#include <linux/compiler.h> /* need __user */
 
 #define HAVE_V4L2 1