virtio-pci: Add lookup subregion of VirtIOPCIRegion MR

virtio-pci: Add lookup subregion of VirtIOPCIRegion MR

Now virtio_address_space_lookup only lookup common/isr/device/notify
MR and exclude their subregions.

When VHOST_USER_PROTOCOL_F_HOST_NOTIFIER enable, the notify MR has
host-notifier subregions and we need use host-notifier MR to
notify the hardware accelerator directly instead of eventfd notify.

Further more, maybe common/isr/device MR also has subregions in
the future, so need memory_region_find for each MR incluing
their subregions.

Add lookup subregion of VirtIOPCIRegion MR instead of only lookup container MR.

Fixes: a93c8d8 ("virtio-pci: Replace modern_as with direct access to modern_bar")
Co-developed-by: Zuo Boqun <zuoboqun@baidu.com>
Signed-off-by: Gao Shiyuan <gaoshiyuan@baidu.com>
Signed-off-by: Zuo Boqun <zuoboqun@baidu.com>
Message-Id: <20240903120304.97833-1-gaoshiyuan@baidu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>