drivers/hid/uhid.c: check write() bitness using in_compat_syscall

uhid changes the format expected in write() depending on bitness.  It
should check the syscall bitness directly.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: David Herrmann <dh.herrmann@googlemail.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>