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initclocks: don't reinitialize ticks, jiffies at runtime

Various drivers use ticks/jiffies before initclocks().  It isn't
generally safe to reinitialize them at runtime.  Hoist the conditional
definition of HZ from param.c into sys/kernel.h so we can see it from
kern_clock.c and statically initialize ticks/jiffies to the desired
offset.

With this change, timeouts scheduled before initclocks() do not all
fire immediately during the first softclock().

With input from kettenis@.

Link: https://marc.info/?l=openbsd-tech&m=167753870803378&w=2

/*	$OpenBSD: kernel.h,v 1.26 2023/03/03 20:16:44 cheloha Exp $	*/
/*	$NetBSD: kernel.h,v 1.11 1995/03/03 01:24:16 cgd Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *	@(#)kernel.h	8.3 (Berkeley) 1/21/94
 */

/* Global variables for the kernel. */

/* 1.1 */
extern long hostid;
extern char hostname[MAXHOSTNAMELEN];
extern int hostnamelen;
extern char domainname[MAXHOSTNAMELEN];
extern int domainnamelen;

/* 1.2 */
extern int utc_offset;		/* seconds east of UTC */

extern int tick;		/* usec per tick (1000000 / hz) */
extern int tick_nsec;		/* nsec per tick */
extern int ticks;		/* # of hardclock ticks */
extern int hz;			/* system clock's frequency */
extern int stathz;		/* statistics clock's frequency */
extern int profhz;		/* profiling clock's frequency */
extern int lbolt;		/* once a second sleep address */

#ifndef HZ
#define HZ 100
#endif