pinctrl: add function to parse generic pinconfig properties from a dt node

pinconf_generic_parse_dt_config() takes a node as input and generates an
array of generic pinconfig values from the properties of this node.

As I couldn't find a mechanism to count the number of properties of a node
the function uses internally an array to accept one of parameter and copies
the real present options to a smaller variable at its end.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/pinconf.h b/drivers/pinctrl/pinconf.h
index 92c7267..a4a5417 100644
--- a/drivers/pinctrl/pinconf.h
+++ b/drivers/pinctrl/pinconf.h
@@ -123,3 +123,9 @@
 	return;
 }
 #endif
+
+#if defined(CONFIG_GENERIC_PINCONF) && defined(CONFIG_OF)
+int pinconf_generic_parse_dt_config(struct device_node *np,
+				    unsigned long **configs,
+				    unsigned int *nconfigs);
+#endif