soc/tegra: pmc: Fix crashes for hierarchical interrupts

Interrupts that don't have an associated wake event or GPIO wake events
end up with an associate IRQ chip that is NULL and which causes IRQ code
to crash. This is because we don't implicitly set the parent IRQ chip by
allocating the interrupt at the parent. However, there really isn't a
corresponding interrupt at the parent, so we need to work around this by
setting the special no_irq_chip as the IRQ chip for these interrupts.

Fixes: 19906e6b ("soc/tegra: pmc: Add wake event support")
Signed-off-by: Thierry Reding <treding@nvidia.com>