gpio: vf610: switch to dynamic allocat GPIO base

gpiolib want to get completely rid of static gpiobase allocation,
so switch to dynamic allocat GPIO base, also can avoid warning
message:

[    1.529974] gpio gpiochip0: Static allocation of GPIO base
is deprecated, use dynamic allocation.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>