qdev: gpio: Define qdev_pass_gpios()

qdev: gpio: Define qdev_pass_gpios()

Allows a container to take ownership of GPIOs in a contained
device and automatically connect them as GPIOs to the container.

This prepares for deprecation of the SYSBUS IRQ functionality, which
has this feature. We push it up to the device level instead of sysbus
level. There's nothing sysbus specific about passing GPIOs to
containers so its a legitimate device-level generic feature.

Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>