powerpc: Only print PACATMSCRATCH in oops when TM is active

If TM is not active there is no need to print PACATMSCRATCH
so we can save ourselves a line.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>