userfaultfd: selftest: update userfaultfd x86 32bit syscall number

It changed as result of other syscalls, and while the system call list
itself was correctly updated, the selftest program was not.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>