npf: Eliminate __HAVE_ATOMIC_AS_MEMBAR conditionals.

Discussed on tech-kern:
https://mail-index.netbsd.org/tech-kern/2023/02/23/msg028729.html

Requested by rmind@:
rmind/npf#127 (comment)

Author: riastradh

sys/net/npf/npf_nat.c

@@ -67,7 +67,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_nat.c,v 1.52 2022/04/09 23:38:33 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_nat.c,v 1.53 2023/02/24 11:03:01 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -279,15 +279,11 @@ npf_natpolicy_release(npf_natpolicy_t *np)
 {
 	KASSERT(atomic_load_relaxed(&np->n_refcnt) > 0);
 
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 	membar_release();
-#endif
 	if (atomic_dec_uint_nv(&np->n_refcnt) != 0) {
 		return;
 	}
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 	membar_acquire();
-#endif
 	KASSERT(LIST_EMPTY(&np->n_nat_list));
 	mutex_destroy(&np->n_lock);
 	kmem_free(np, sizeof(npf_natpolicy_t));

sys/net/npf/npf_rproc.c

@@ -33,7 +33,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_rproc.c,v 1.22 2022/04/09 23:38:33 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_rproc.c,v 1.23 2023/02/24 11:03:01 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -330,15 +330,12 @@ npf_rproc_release(npf_rproc_t *rp)
 {
 	KASSERT(atomic_load_relaxed(&rp->rp_refcnt) > 0);
 
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 	membar_release();
-#endif
 	if (atomic_dec_uint_nv(&rp->rp_refcnt) != 0) {
 		return;
 	}
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 	membar_acquire();
-#endif
+
 	/* XXXintr */
 	for (unsigned i = 0; i < rp->rp_ext_count; i++) {
 		npf_ext_t *ext = rp->rp_ext[i];

sys/net/npf/npf_tableset.c

@@ -46,7 +46,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_tableset.c,v 1.41 2023/01/23 13:40:04 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_tableset.c,v 1.42 2023/02/24 11:03:01 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -160,14 +160,10 @@ npf_tableset_destroy(npf_tableset_t *ts)
 
 		if (t == NULL)
 			continue;
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 		membar_release();
-#endif
 		if (atomic_dec_uint_nv(&t->t_refcnt) > 0)
 			continue;
-#ifndef __HAVE_ATOMIC_AS_MEMBAR
 		membar_acquire();
-#endif
 		npf_table_destroy(t);
 	}
 	kmem_free(ts, NPF_TABLESET_SIZE(ts->ts_nitems));