pf: Use a macro to get the hash row in pf_find_state_byid()

This seems a bit preferable to open-coding it.  No functional change
intended.

Reviewed by:	kp, glebius
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D49518

Author: markjdb

sys/net/pfvar.h

@@ -2226,7 +2226,8 @@ VNET_DECLARE(struct pf_udpendpointhash *, pf_udpendpointhash);
 VNET_DECLARE(struct pf_srchash *, pf_srchash);
 #define	V_pf_srchash	VNET(pf_srchash)
 
-#define PF_IDHASH(s)	(be64toh((s)->id) % (V_pf_hashmask + 1))
+#define	PF_IDHASHID(id)	(be64toh(id) % (V_pf_hashmask + 1))
+#define	PF_IDHASH(s)	PF_IDHASHID((s)->id)
 
 VNET_DECLARE(void *, pf_swi_cookie);
 #define V_pf_swi_cookie	VNET(pf_swi_cookie)

sys/netpfil/pf/pf.c

@@ -1864,7 +1864,7 @@ pf_find_state_byid(uint64_t id, uint32_t creatorid)
 
 	pf_counter_u64_add(&V_pf_status.fcounters[FCNT_STATE_SEARCH], 1);
 
-	ih = &V_pf_idhash[(be64toh(id) % (V_pf_hashmask + 1))];
+	ih = &V_pf_idhash[PF_IDHASHID(id)];
 
 	PF_HASHROW_LOCK(ih);
 	LIST_FOREACH(s, &ih->states, entry)