pseries: Split device tree construction from device tree load

pseries: Split device tree construction from device tree load

spapr_finalize_fdt() both finishes building the device tree for the guest
and loads it into guest memory.  For future cleanups, it's going to be
more convenient to do these two things separately.  The loading portion is
pretty trivial, so we move it inline into the caller, ppc_spapr_reset().

We also rename spapr_finalize_fdt(), because the current name is going to
become inaccurate.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>