irqchip/msi-lib: Fix fwnode refcount in msi_lib_irq_domain_select()

Commit 8b65db1e ("irqchip/msi-lib: Add IRQ_DOMAIN_FLAG_FWNODE_PARENT
handling") added logic in msi_lib_irq_domain_select() to match the domain
fwnode against the fwnode parent of the fwspec.fwnode.

The fwnode_get_parent() caller must call fwnode_handle_put() on the
returned pointer value, lest fwnode refcounting for the parent ends up
being out of kilter.

Fix this by relying on the fwnode_handle clean-up handlers and by
incrementing the fwnode refcount regardless of whether parent matching is
used or not (the domain selection code already holds a reference before
calling msi_lib_irq_domain_select() but to make the exit path more uniform
if IRQ_DOMAIN_FLAG_FWNODE_PARENT is not set fwnode_handle_get() is called
again on fwspec.fwnode so that the clean-up code is the same for the two
matching patterns).

Fixes: 8b65db1e ("irqchip/msi-lib: Add IRQ_DOMAIN_FLAG_FWNODE_PARENT handling")
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250804145553.795065-1-lpieralisi@kernel.org