hostap: Revert a toxic part of the conversion to net_device_ops

As the hostap driver was converted to use net_device_ops, a mistake was
made in hostap_main.c (commit 5ae4efbc).
Originally, the tx_queue_len was set to 0 for every other interface than
HOSTAP_INTERFACE_MASTER, but the new fragment of code sets tx_queue_len to
0 only for HOSTAP_INTERFACE_MASTER. The opposite of the previous
behavior makes the driver to drop all packets in AP mode.

Change the way 0 is assigned to tx_queue_len according to the original
logic.

Signed-off-by: Martin Decky <martin@decky.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>