USB: wdm: close race between wdm_open and wdm_wwan_port_stop

USB: wdm: close race between wdm_open and wdm_wwan_port_stop

commit c1846ed4eb527bdfe6b3b7dd2c78e2af4bf98f4f upstream.

Clearing WDM_WWAN_IN_USE must be the last action or
we can open a chardev whose URBs are still poisoned

Fixes: cac6fb015f71 ("usb: class: cdc-wdm: WWAN framework integration")
Cc: stable <stable@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20250401084749.175246-3-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>