ppc: Provide basic raise_exception_* functions

ppc: Provide basic raise_exception_* functions

Instead of using the same helpers called from translate.c, let's have
a bunch of functions that take the various argument combinations,
especially the retaddr which will be needed in subsequent patches,
and leave the helpers to be just that, helpers for translate.c

We don't yet convert all users, we'll go through them in subsequent
patches.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
--

v2. Fix raise_exception_ra() to properly pass raddr
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>