fs: compat: Remove warning from COMPATIBLE_IOCTL

cmd in COMPATIBLE_IOCTL is always a u32, so cast it so there isn't a
warning about an overflow in XFORM.

From: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/compat_ioctl.c

@@ -833,7 +833,7 @@ static int compat_ioctl_preallocate(struct file *file,
  */
 #define XFORM(i) (((i) ^ ((i) << 27) ^ ((i) << 17)) & 0xffffffff)
 
-#define COMPATIBLE_IOCTL(cmd) XFORM(cmd),
+#define COMPATIBLE_IOCTL(cmd) XFORM((u32)cmd),
 /* ioctl should not be warned about even if it's not implemented.
    Valid reasons to use this:
    - It is implemented with ->compat_ioctl on some device, but programs