irqchip/gic-v3-its-platform-msi: Fix msi-parent parsing loop

irqchip/gic-v3-its-platform-msi: Fix msi-parent parsing loop

While parsing the msi-parent property to chase up the IRQ domain
a given device belongs to, the index into the msi-parent tuple should
be incremented to ensure all properties entries are taken into account.

Current code missed the index update so the parsing loop does not work
in case multiple msi-parent phandles are present and may turn into
an infinite loop in of_pmsi_get_dev_id() if phandle at index 0 does
not correspond to the domain we are actually looking-up.

Fix the code by updating the phandle index at each iteration in
of_pmsi_get_dev_id().

Fixes: 8a837ed688b9 ("irqchip/gic-v3-its: Parse new version of msi-parent property")
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>