sparc: Enable VDSO for static linking

Checked on sparc64-linux-gnu and sparcv9-linux-gnu.

	[BZ #19767]
	* sysdeps/unix/sysv/linux/sparc/init-first.c: Remove #ifdef SHARED.
	* sysdeps/unix/sysv/linux/sparc/libc-vdso.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sysdep.h (ALWAYS_USE_VSYSCALL):
	Define.