powerpc: Use the TRAP macro whenever comparing a trap number

Trap numbers can have extra bits at the bottom that need to
be filtered out. There are a few cases where we don't do that.

It's possible that we got lucky but better safe than sorry.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>