Include the now missing headers after untangling if.h and if_var.h.

This fixes pc98 build.

Reviewed by:	andre

sys/dev/snc/if_snc.c

@@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$");
 #include <net/if.h>
 #include <net/if_arp.h>
 #include <net/if_media.h>
+#include <net/if_var.h>
 
 #include <dev/snc/dp83932reg.h>
 #include <dev/snc/dp83932var.h>

sys/dev/snc/if_snc_pccard.c

@@ -41,6 +41,8 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/socket.h>
 #include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
 
 #include <sys/module.h>
 #include <sys/bus.h>