pinctrl: core: Add generic pinctrl functions for managing groups

We can add generic helpers for function handling for cases where the pin
controller driver does not need to use static arrays.

Signed-off-by: Tony Lindgren <tony@atomide.com>
[Renamed the Kconfig item and moved things around]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index add257f..7e96428 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -14,6 +14,10 @@
 config PINMUX
 	bool "Support pin multiplexing controllers" if COMPILE_TEST
 
+config GENERIC_PINMUX_FUNCTIONS
+	bool
+	select PINMUX
+
 config PINCONF
 	bool "Support pin configuration controllers" if COMPILE_TEST