getpagesizes(3): drop support for kernels before 9.0

AT_PAGESIZES and elf_aux_info where added prior to FreeBSD 9.0 in commit
ee235be.  It's safe to say that a
FreeBSD 15 libc won't work on a 8.x kernel so drop sysctl fallback.

Reviewed by:	kevans, imp, emaste
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42707

lib/libc/gen/getpagesizes.c

@@ -27,11 +27,8 @@
  */
 
 #include <sys/param.h>
-#include <sys/mman.h>
-#include <sys/sysctl.h>
-
-#include <errno.h>
-#include <link.h>
+#include <sys/auxv.h>
+#include <sys/errno.h>
 
 #include "libc_private.h"
 
@@ -52,24 +49,18 @@ getpagesizes(size_t pagesize[], int nelem)
 {
 	static u_long ps[MAXPAGESIZES];
 	static int nops;
-	size_t size;
-	int error, i;
+	int i;
 
 	if (nelem < 0 || (nelem > 0 && pagesize == NULL)) {
 		errno = EINVAL;
 		return (-1);
 	}
-	/* Cache the result of the sysctl(2). */
+	/* Cache the result */
 	if (nops == 0) {
-		error = _elf_aux_info(AT_PAGESIZES, ps, sizeof(ps));
-		size = sizeof(ps);
-		if (error != 0 || ps[0] == 0) {
-			if (sysctlbyname("hw.pagesizes", ps, &size, NULL, 0)
-			    == -1)
-				return (-1);
-		}
+		if (_elf_aux_info(AT_PAGESIZES, ps, sizeof(ps)) != 0)
+			ps[0] = PAGE_SIZE;
 		/* Count the number of page sizes that are supported. */
-		nops = size / sizeof(ps[0]);
+		nops = nitems(ps);
 		while (nops > 0 && ps[nops - 1] == 0)
 			nops--;
 	}