ppc/85xx: Clean up do_reset

There is no reason to do a run time check for e500 v1 based cores to
determine if we have the GUTs RSTCR facility.  Only the first generation
of PQ3 parts (MPC8540/41/55/60) do not have it.  So checking to see if
we are e500 v2 would miss future parts (like e500mc).

Just change this to be ifdef'd based on CONFIG_MPC85{40,41,55,60}.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>