net: wwan: core: split port unregister and stop

net: wwan: core: split port unregister and stop

Upcoming GNSS (NMEA) port type support requires exporting it via the
GNSS subsystem. On another hand, we still need to do basic WWAN core
work: call the port stop operation, purge queues, release the parent
WWAN device, etc. To reuse as much code as possible, split the port
unregistering function into the deregistration of a regular WWAN port
device, and the common port tearing down code.

In order to keep more code generic, break the device_unregister() call
into device_del() and put_device(), which release the port memory
uniformly.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Reviewed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
Link: https://patch.msgid.link/20260126062158.308598-5-slark_xiao@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>