Update syscall lists for Linux 5.15

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.