arm64: Update __NR_compat_syscalls for statmount/listmount

Commit d8b0f546 ("wire up syscalls for statmount/listmount") added
two new system calls to arch/arm64/include/asm/unistd32.h but forgot to
update the __NR_compat_syscalls number, thus causing the following build
failures:

  arch/arm64/include/asm/unistd32.h:922:24: error: array index in initializer exceeds array bounds
    922 | #define __NR_statmount 457
        |                        ^~~
  arch/arm64/kernel/sys32.c:130:34: note: in definition of macro '__SYSCALL'
    130 | #define __SYSCALL(nr, sym)      [nr] = __arm64_##sym,
        |                                  ^~

Bump up the number by two to accomodate for the new system calls added.

Fixes: d8b0f546 ("wire up syscalls for statmount/listmount")
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>