BUG: headers with BUG/BUG_ON etc. need linux/bug.h

If a header file is making use of BUG, BUG_ON, BUILD_BUG_ON, or any
other BUG variant in a static inline (i.e. not in a #define) then
that header really should be including <linux/bug.h> and not just
expecting it to be implicitly present.

We can make this change risk-free, since if the files using these
headers didn't have exposure to linux/bug.h already, they would have
been causing compile failures/warnings.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/include/net/udp.h b/include/net/udp.h
index e39592f..5d606d9 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -23,6 +23,7 @@
 #define _UDP_H
 
 #include <linux/list.h>
+#include <linux/bug.h>
 #include <net/inet_sock.h>
 #include <net/sock.h>
 #include <net/snmp.h>