linux: Enable vDSO for static linking as default (BZ#19767)

This patch assumes static vDSO is supported as default, it is now supported
on all current architectures that support vDSO.  It allows removing both
ALWAYS_USE_VSYSCALL define, which an architecture requires to explicit define
and USE_VSYSCALL (which defines vDSO only for shared or if architecture defines
ALWAYS_USE_VSYSCALL).

Checked with a build against all affected ABIs.

	[BZ #19767]
	* sysdeps/unix/sysv/linux/aarch64/sysdep.h (ALWAYS_USE_VSYSCALL):
	Remove definition.
	* sysdeps/unix/sysv/linux/arm/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/i386/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/riscv/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
	(ALWAYS_USE_VSYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/sparc/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/sysdep.h (ALWAYS_USE_VSYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/x86/libc-vdso.h: Remove #if USE_VSYSCALL.
	* sysdeps/unix/sysv/linux/sysdep-vdso.h: Likewise.
	* sysdeps/unix/sysv/linux/sysdep.h (ALWAYS_USE_VSYSCALL,
	USE_VSYSCALL): Remove defitions.