reset: Silence warning in reset-controller.h

If a user of <linux/reset-controller.h> doesn't include
<linux/of.h> before including reset-controller.h they'll get a
warning as follows:

include/linux/reset-controller.h:44:17:
warning: 'struct of_phandle_args' declared inside parameter list

This is because of_phandle_args is not forward declared. Add the
declaration to silence this warning.

Acked-by: Philipp Zabel <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

include/linux/reset-controller.h

···
 
 struct module;
 struct device_node;
+struct of_phandle_args;
 
 /**
  * struct reset_controller_dev - reset controller entity that might