pcihp: compose PCNT callchain right before its user _GPE._E01

pcihp: compose PCNT callchain right before its user _GPE._E01

it's a stepping stone to making build_append_pci_bus_devices() suitable
for AcpiDevAmlIfClass:build_dev_aml callback and lets further simplify
it by separating PCNT generation from slots descriptions.

It also makes PCNT callchain ASL much more readable since callchain
not longer cluttered by slots descriptors.

Plus, move will let next patch easily drop empty PCNT (pc/q35)
when there is nothing hotpluggable.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20230112140312.3096331-22-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>