bug.h: add include of it to various implicit C users

With bug.h currently living right in linux/kernel.h there
are files that use BUG_ON and friends but are not including
the header explicitly.  Fix them up so we can remove the
presence in kernel.h file.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/lib/list_debug.c b/lib/list_debug.c
index 7204e61..1bf2fe3 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -8,6 +8,7 @@
 
 #include <linux/module.h>
 #include <linux/list.h>
+#include <linux/bug.h>
 #include <linux/kernel.h>
 
 /*