Add a GPIO driver for the Gateworks Cambria platform.

Add a GPIO driver for the Gateworks Cambria platform.

The external gpio pins are connected to a PLD on the i2c bus, unfortunatley
this device does not conform by failing to send an ack after each byte written.
The iicbb driver will abort the transfer when the address is not ack'd and it
would introduce a lot of churn to be able to pass a flag down to
iicbb_start/iicbb_write. Instead we do bad things by grabbing the iicbus but
then doing our own bit banging.