posix: Consolidate Linux msync syscall

posix: Consolidate Linux msync syscall

This patch consolidates the msync Linux syscall generation on
sysdeps/unix/sysv/linux/msync.c.  It basically removes it from
architectures auto-generation list.

Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu,
sparc64-linux-gnu, and sparcv9-linux-gnu.

	* misc/Makefile (CFLAGS-msync.c): New rule.
	* nptl/Makefile (CFLAGS-msync.c): Likewise.
	* sysdeps/unix/syscalls.list: Remove msync from auto-generation list.
	* sysdeps/unix/sysv/linux/msync.c: New file.