pinctrl: generic: change signature of pinctrl_generic_to_map() to pass void data

pinctrl: generic: change signature of pinctrl_generic_to_map() to pass void data

In order to make pinctrl_generic_to_map() usable for controllers that
use pinmux, change the functions char array pointer that it passes to
pinctrl_generic_add_group() to a void pointer. In the pinmux case this
property will contain the mux setting as a number rather than as strings
in the pins + functions case.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>