reset: hi6220: fix modular build

We need to include <linux/module.h> to build the driver as a loadable
module:

drivers/reset/hisilicon/hi6220_reset.c:108:1: warning: data definition has no type or storage class
 postcore_initcall(hi6220_reset_init);

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/reset/hisilicon/hi6220_reset.c

@@ -12,6 +12,7 @@
 
 #include <linux/io.h>
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/bitops.h>
 #include <linux/of.h>
 #include <linux/reset-controller.h>