gpio: pl061: add DT binding support

This adds devicetree binding support to the ARM pl061 driver removing the
platform_data dependency. When DT binding is used, the gpio numbering is
assigned dynamically. For now, interrupts are not supported with DT until
irqdomains learn dynamic irq assignment.

Rather than add another case of -1, updating the driver to use NO_IRQ.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>