pinctrl: cygnus: Remove GPIO to Pinctrl pin mapping from driver

Remove gpio to pinctrl pin mapping code from driver and
address this through standard property "gpio-ranges".

Signed-off-by: Pramod Kumar <pramodku@broadcom.com>
Reviewed-by: Ray Jui <rjui@broadcom.com>
Reviewed-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>