Now that we have a function that implements the complexity of the
"msi-parent" property parsing, switch to that.
Acked-by: NRob Herring <robh@kernel.org>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>