pinctrl: rza1: Remove suffix from gpiochip label

The OF node name already contains the gpio chip identifier, no need to
append it when creating the label.

The following debug message clearly shows the suffix is not required
"pinctrl-rza1 fcfe3000.pin-controller: Parsed gpiochip gpio-0-0 with 6
pins"

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>