pin_to_mask expects a bank pin number. So do not add the chip base.

Without that patch cat /sys/kernel/debug/gpio looks like that:
GPIOs 0-31, platform/fffff200.gpio, fffff200.gpio:
[spi32766.0] GPIOfffff200.gpio5: [gpio] set
[ads7846_pendown] GPIOfffff200.gpio15: [gpio] set
[ohci_vbus] GPIOfffff200.gpio21: [gpio] set
[ohci_vbus] GPIOfffff200.gpio24: [gpio] set
[button1] GPIOfffff200.gpio28: [gpio] clear
[button2] GPIOfffff200.gpio29: [gpio] clear

GPIOs 32-63, platform/fffff400.gpio, fffff400.gpio:
[sda] GPIOfffff400.gpio4: [periph A]
[scl] GPIOfffff400.gpio5: [periph A]
[spi32766.3] GPIOfffff400.gpio11: [periph A]
[error] GPIOfffff400.gpio22: [periph A]
[run] GPIOfffff400.gpio23: [periph A]

GPIOs 64-95, platform/fffff600.gpio, fffff600.gpio:
[reset_pin] GPIOfffff600.gpio29: [periph A]

GPIOs 96-127, platform/fffff800.gpio, fffff800.gpio:
[led1] GPIOfffff800.gpio5: [periph A]
[led2] GPIOfffff800.gpio6: [periph A]
[led3] GPIOfffff800.gpio7: [periph A]
[led4] GPIOfffff800.gpio8: [periph A]

GPIOs 128-159, platform/fffffa00.gpio, fffffa00.gpio:
[button3] GPIOfffffa00.gpio10: [periph A]
[button4] GPIOfffffa00.gpio12: [periph A]

Note that every bank despite bank 0 only shows "periph A" which are
obviously used as GPIOs.
Signed-off-by: Alexander Stein <alexanders83@web.de>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>