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/bitmap.c b/lib/bitmap.c
index 0d4a127..90a683b 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -10,6 +10,7 @@
 #include <linux/errno.h>
 #include <linux/bitmap.h>
 #include <linux/bitops.h>
+#include <linux/bug.h>
 #include <asm/uaccess.h>
 
 /*