print_setsockopt: fix fall-through bug in SOL_IP switch case

This fixes the bug introduced by commit v4.9-250-ga0a4909.

* net.c (print_setsockopt): Separate SOL_IP case from SOL_PACKET.

Reported-by: Ben Noordhuis <info@bnoordhuis.nl>
diff --git a/net.c b/net.c
index 49185dc..cb29faa 100644
--- a/net.c
+++ b/net.c
@@ -1445,6 +1445,7 @@
 			goto done;
 #endif /* MCAST_JOIN_GROUP */
 		}
+		break;
 
 	case SOL_PACKET:
 		switch (name) {