[POWERPC] Make instruction dumping work in real mode

On non-book-E, exceptions execute in real mode.  If a fault happens
that leads to a register dump, the kernel currently prints XXXXXXXX
because it doesn't realize that PC is a physical address.

This patch checks whether instruction address translation is turned
on, and if not converts PC into a virtual address.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>