gpio: altera-a10sr: Add A10 System Resource Chip GPIO support.

Add the GPIO functionality for the Altera Arria10 MAX5 System Resource
Chip. The A10 MAX5 has 12 bits of GPIO assigned to switches, buttons,
and LEDs as a GPIO extender on the SPI bus.

Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org&gt;i>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>