soc/tegra: pmc: Don't create fake interrupt hierarchy levels

The Tegra PMC driver does ungodly things with the interrupt hierarchy,
repeatedly corrupting it by pulling hwirq numbers out of thin air,
overriding existing IRQ mappings and changing the handling flow
of unsuspecting users.

All of this is done in the name of preserving the interrupt hierarchy
even when these levels do not exist in the HW. Together with the use
of proper IRQs for IPIs, this leads to an unbootable system as the
rescheduling IPI gets repeatedly repurposed for random drivers...

Instead, let's simply mark the level from which the hierarchy does
not make sense for the HW, and let the core code trim the usused
levels from the hierarchy.

Signed-off-by: Marc Zyngier <maz@kernel.org>