pseries: Use new method to correct reset sequence

A number of things need to occur during reset of the PAPR
paravirtualized platform in a specific order.  For example, the hash
table needs to be cleared before the CPUs are reset, so that they
initialize their register state correctly, and the CPUs need to have
their main reset called before we set up the entry point state on the
boot cpu.  We also need to have the main qdev reset happen before the
creation and installation of the device tree for the new boot, because
we need the state of the devices settled to correctly construct the
device tree.

We currently do the pseries once-per-reset initializations done from a
reset handler.  However we can't adequately control when this handler
is called during the reset - in particular we can't guarantee it
happens after all the qdev resets (since qdevs might be registered
after the machine init function has executed).

This patch uses the new QEMUMachine reset method to to fix this
problem, ensuring the various order dependent reset steps happen in
the correct order.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
