target/ppc: Standardize instance_init and realize function names

target/ppc: Standardize instance_init and realize function names

Because of the various hooks called some variant on "init" - and the rather
greater number that used to exist, I'm always wondering when a function
called simply "*_init" or "*_initfn" will be called.

To make it easier on myself, and maybe others, rename the instance_init
hooks for ppc cpus to *_instance_init().  While we're at it rename the
realize time hooks to *_realize() (from *_realizefn()) which seems to be
the more common current convention.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>