genirq/msi: Allow creation of a tree-based irqdomain for platform-msi

platform_msi_create_device_domain() always creates a revmap-based
irqdomain, which has the drawback of requiring the number of MSIs
that can be allocated ahead of time. This is not always possible,
and we sometimes need to use a tree-based irqdomain instead.

Add a new platform_msi_create_device_tree_domain() helper to
that effect.

Reported-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>