Consolidate Linux semtimedop implementation

This patch consolidates the semtimedop Linux implementation in only
one default file, sysdeps/unix/sysv/linux/semtimedop.c.  If tries to use
the direct syscall if it is supported, otherwise will use the old ipc
multiplex mechanism.

Checked on x86_64, i686, powerpc64le, aarch64, and armhf.

	* sysdeps/unix/sysv/linux/alpha/syscalls.list (semtimedop): Remove.
	* sysdeps/unix/sysv/linux/arm/syscalls.list (semtimedop): Likewise.
	* sysdeps/unix/sysv/linux/generic/syscalls.list (semtimedop):
	Likewise.
	* sysdeps/unix/sysv/linux/hppa/syscalls.list (semtimedop): Likewise.
	* sysdeps/unix/sysv/linux/ia64/syscalls.list (semtimedop): Likewise.
	* sysdeps/unix/sysv/linux/microblaze/syscalls.list (semtimedop):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/syscalls.list (semtimedop):
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/syscalls.list (semtimedop): Likewise.
	* sysdeps/unix/sysv/linux/m68k/semtimedop.S: Remove file.
	* sysdeps/unix/sysv/linux/s390/semtimedop.c: Reorganize headers and
	add a comment about s390 syscall difference from default one.
	* sysdeps/unix/sysv/linux/semtimedop.c (semtimedop): Use semtimedop
	syscall if it is defined.