pinctrl: mvebu: armada-39x: fix incorrect total number of GPIOs

The pinctrl_gpio_range[] array described a first bank of 32 GPIOs and
a second one of 27 GPIOs. However, since there is a total of 60 MPP
pins that can be muxed as GPIOs, the second bank really has 28 GPIOs.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: <stable@vger.kernel.org> # v4.1+
Fixes: ee086577 ("pinctrl: mvebu: add pinctrl driver for Marvell Armada 39x")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>