ppc/pnv: fix QOM parenting of user creatable root ports

ppc/pnv: fix QOM parenting of user creatable root ports

User creatable root ports are being parented by the 'peripheral' or the
'peripheral-anon' container. This happens because this is the regular
QOM schema for sysbus devices that are added via the command line.

Let's make this QOM hierarchy similar to what we have with default root
ports, i.e. the root port must be parented by the pnv-root-bus. To do
that we change the qom and bus parent of the root port during
root_port_realize(). The realize() is shared by the default root port
code path, so we can remove the code inside pnv_phb_attach_root_port()
that was adding the root port as a child of the bus as well.

After all that, remove pnv_phb_attach_root_port() and create the root
port explictly in the 'default_enabled()' case of pnv_phb_realize().

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Message-Id: <20220819094748.400578-3-danielhb413@gmail.com>