Though this block of code is not used by FreeBSD, correct a call to

sprintf() with a macro call to SNPRINTF similar to other calls to
SNPRINTF within this same block.

MFC after:	1 week

sys/contrib/ipfilter/netinet/ip_ftp_pxy.c

@@ -2136,7 +2136,7 @@ ipf_p_ftp_eprt6(softf, fin, ip, nat, ftp, dlen)
 	SNPRINTF(s, left, "%x:%x", a >> 16, a & 0xffff);
 	left -= strlen(s);
 	s += strlen(s);
-	sprintf(s, "|%d|\r\n", port);
+	SNPRINTF(s, left, "|%d|\r\n", port);
 #else
 	(void) sprintf(s, "EPRT %c2%c", delim, delim);
 	s += strlen(s);