regmap: Add another missing header for !CONFIG_REGMAP stubs

commit 3f0fa9a upstream.

The use of WARN_ON() needs the definitions from bug.h, without it
you can get:

include/linux/regmap.h: In function 'regmap_write':
include/linux/regmap.h:525:2: error: implicit declaration of function 'WARN_ONCE' [-Werror=implicit-function-declaration]

Signed-off-by: Kevin Hilman <[email protected]>
Signed-off-by: Mark Brown <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Kevin Hilman

include/linux/regmap.h

@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/rbtree.h>
 #include <linux/err.h>
+#include <linux/bug.h>
 
 struct module;
 struct device;