libc: remove unused stub vdso timecounter implementations

All supported architectures have shared page support so remove this
unused stub.

Reviewed by:	imp, kib
Differential Revision:	https://reviews.freebsd.org/D42619

lib/libc/sys/trivial-vdso_tc.c

@@ -1,45 +0,0 @@
-/*-
- * Copyright (c) 2013 Konstantin Belousov <kib@FreeBSD.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <sys/types.h>
-#include <sys/time.h>
-#include <sys/vdso.h>
-#include <errno.h>
-
-#pragma weak __vdso_gettc
-int
-__vdso_gettc(const struct vdso_timehands *th, u_int *tc)
-{
-
-	return (ENOSYS);
-}
-
-#pragma weak __vdso_gettimekeep
-int
-__vdso_gettimekeep(struct vdso_timekeep **tk)
-{
-
-	return (ENOSYS);
-}