usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach

This patch replaces the usage of netif_stop_queue with netif_device_detach
in the u_ether driver. The netif_device_detach function not only stops all
tx queues by calling netif_tx_stop_all_queues but also marks the device as
removed by clearing the __LINK_STATE_PRESENT bit.

This change helps notify user space about the disconnection of the device
more effectively, compared to netif_stop_queue, which only stops a single
transmit queue.

Signed-off-by: Hardik Gajjar <hgajjar@de.adit-jv.com>
Link: https://lore.kernel.org/r/20231006155646.12938-1-hgajjar@de.adit-jv.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>