of: unify of_count_phandle_with_args() arguments with !CONFIG_OF

Unify the declaration of of_count_phandle_with_args() between enabled
and disabled OF by making constifying pointed device_node.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

include/linux/of.h

@@ -896,7 +896,7 @@ static inline int of_parse_phandle_with_fixed_args(const struct device_node *np,
 	return -ENOSYS;
 }
 
-static inline int of_count_phandle_with_args(struct device_node *np,
+static inline int of_count_phandle_with_args(const struct device_node *np,
 					     const char *list_name,
 					     const char *cells_name)
 {