irqchip/apple-aic: Correctly map the vgic maintenance interrupt

irqchip/apple-aic: Correctly map the vgic maintenance interrupt

We currently allocate the vgic maintenance interrupt by calling into
the low-level irqdomain code. Not only this is unnecessary, but this
is also pretty wrong: we end-up skipping a bunch of irqdesc state
setup

A simple "cat /proc/interrupt" shows how wrong we are, as the
interrupt appears as "Edge" instead of "Level".

Instead, just call the standard irq_create_fwspec_mapping(), which
is the right tool for the job. Duh.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Hector Martin <marcan@marcan.st>
Link: https://lore.kernel.org/r/20230201164056.669509-1-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>