Enable VDSO for static linking on arm

I have tested that this builds and the resulting program still work.
The kernel in gcc117 (which I ussed for testing) seems to be missing
https://patchwork.kernel.org/patch/10060431/, so the vdso is never used.

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