pinctrl/u300/coh901: let the gpio_chip register the range

Instead of having the pinctrl driver register the GPIO range
for the gpio_chip, making it necessary to instantiate the
pin controller from the GPIO driver and pass the GPIO chip as
platform data, now let the GPIO chip driver register it's own
ranges and have the pinctrl driver look up the GPIO chip from
the pinctrl core as necessary.

Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>