alpha-linux-user: Fix umount syscall numbers

It has been pointed out on LKML that the alpha umount syscall numbers
are named wrong, and a patch to rectify that has been posted for 3.11.

Glibc works around this by treating NR_umount as NR_umount2 if
NR_oldumount exists.  That's more complicated than we need in QEMU,
given that we control linux-user/*/syscall_nr.h.

This is the last instance of TARGET_NR_oldumount, so delete that from
the strace.list.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips-linux-user: Adjust names in mips_syscall_args

The name field of MIPS_SYS isn't actually used; it's just documentation.
But adjust the umount entries to match mips/syscall_nr.h anyway.

Signed-off-by: Richard Henderson <rth@twiddle.net>