staging: mt7621-pinctrl: stop using the deprecated 'pinctrl_add_gpio_range'

staging: mt7621-pinctrl: stop using the deprecated 'pinctrl_add_gpio_range'

If the gpio DT node has the 'gpio-ranges' property, the range will be
added by the gpio core and doesn't need to be added by the pinctrl
driver.

By having the gpio-ranges property, we can map every pin between
gpio node and pinctrl node and we can stop using the deprecated
pinctrl_add_gpio_range() function.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20201206105333.18428-1-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>