microblaze: remove early_init_dt_scan_cpus() and phyp_dump_*()

Microblaze only has one CPU, it isn't SMP at all.  early_init_dt_scan_cpus()
is effectively just a no-op, so remove it.

Microblaze doesn't support hypervisor assisted dump either, so the phyp stuff
can also go.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Michal Simek <monstr@monstr.eu>