Mark i4b IPR and SPPP drivers as NET_NEEDS_GIANT(), as they both

interface with the network stack but are not yet sufficiently
synchronized to run without the Giant lock.  It migh be possible
to mark the interfaces as IFF_NEEDSGIANT, but I'm unable to test
that configuration and am unfamiliar with the architecture of
i4b.

sys/i4b/driver/i4b_ipr.c

@@ -105,6 +105,8 @@ __FBSDID("$FreeBSD$");
 
 #include <i4b/layer4/i4b_l4.h>
 
+NET_NEEDS_GIANT("i4b_ipr");
+
 #define I4BIPRMTU	1500		/* regular MTU */
 #define I4BIPRMAXMTU	2000		/* max MTU */
 #define I4BIPRMINMTU	500		/* min MTU */

sys/i4b/driver/i4b_isppp.c

@@ -67,6 +67,8 @@ __FBSDID("$FreeBSD$");
 
 #include <i4b/layer4/i4b_l4.h>
 
+NET_NEEDS_GIANT("i4b_isppp");
+
 #define ISPPP_FMT	"isp%d: "
 #define	ISPPP_ARG(sc)	((sc)->sc_if.if_dunit)
 #define	PDEVSTATIC	static