PCI: hv: Allocate a named fwnode instead of an address-based one

To allocate its fwnode that is then used to allocate an irqdomain,
the driver uses irq_domain_alloc_fwnode(), passing it a VA as an
identifier. This is a rather bad idea, as this address ends up
published in debugfs (and we want to move away from VAs there
anyway).

Instead, let's allocate a named fwnode by using the device GUID as
an identifier. It is allegedly unique, and can be traced back to
the original device.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>