KVM: PPC: BookE: Improve irq inject tracepoint

When injecting an IRQ, we only document which IRQ priority (which translates
to IRQ type) gets injected. However, when reading traces you don't necessarily
have all the numbers in your head to know which IRQ really is meant.

This patch converts the IRQ number field to a symbolic name that is in sync
with the respective define. That way it's a lot easier for readers to figure
out what interrupt gets injected.

Signed-off-by: Alexander Graf <agraf@suse.de>