Honor the disabled status by only grabbing resources and returning
when running under FDT.
Add an OFW GPIO compatible bus.  This allows the use of the DTS files to
describe GPIO bindings in the system.

Move the GPIOBUS lock macros to gpiobusvar.h as they are now shared between
the OFW and the non OFW versions of GPIO bus.

Export gpiobus_print_pins() so it can also be used on the OFW GPIO bus.

Approved by:	adrian (mentor, implicit)