[POWERPC] Use lowercase for hex printouts in oops messages.

Use lowercase for hex printouts in oops messages. The number of times I have
tried to copy and paste from an oops into an objdump search...

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>