userfaultfd: register uapi generic syscall (aarch64)

Add the userfaultfd syscalls to uapi asm-generic, it was tested with
postcopy live migration on aarch64 with both 4k and 64k pagesize
kernels.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/uapi/asm-generic/unistd.h

@@ -709,17 +709,19 @@ __SYSCALL(__NR_memfd_create, sys_memfd_create)
 __SYSCALL(__NR_bpf, sys_bpf)
 #define __NR_execveat 281
 __SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat)
-#define __NR_membarrier 282
+#define __NR_userfaultfd 282
+__SYSCALL(__NR_userfaultfd, sys_userfaultfd)
+#define __NR_membarrier 283
 __SYSCALL(__NR_membarrier, sys_membarrier)
 
 #undef __NR_syscalls
-#define __NR_syscalls 283
+#define __NR_syscalls 284
 
 /*
  * All syscalls below here should go away really,
  * these are provided for both review and as a porting
  * help for the C library version.
-*
+ *
  * Last chance: are any of these important enough to
  * enable by default?
  */