Update syscall lists for Linux 5.15

[Florian Weimer]

* Joseph Myers:

> Linux 5.15 has one new syscall, process_mrelease (and also enables the
> clone3 syscall for RV32).  It also has a macro __NR_SYSCALL_MASK for
> Arm, which is not a syscall but matches the pattern used for syscall
> macro names.
>
> Add __NR_SYSCALL_MASK to the names filtered out in the code dealing
> with syscall lists, update syscall-names.list for the new syscall and
> regenerate the arch-syscall.h headers with build-many-glibcs.py
> update-syscalls.
>
> Tested with build-many-glibcs.py.

Looks good to me.

Thanks,
Florian