staging: wfx: fix the warning "inconsistent notification"

staging: wfx: fix the warning "inconsistent notification"

In some circumstances, Tx traffic is sent without associated station but
the station exists when the Tx status is received. Beside that, the
driver keep a counter associated to each station. So, in this case, the
counter is not incremented, but is decremented. In this case a warning
"inconsistent notification" appears:

   ------------[ cut here ]------------
   WARNING: CPU: 3 PID: 82 at /home/jerome/wfx/data_tx.c:469 wfx_skb_dtor+0x1a4/0x1d4 [wfx]
   inconsistent notification
   Modules linked in: [...]
   CPU: 3 PID: 82 Comm: kworker/3:1H Tainted: G         C O      4.19.57-v7l+ #1244
   Hardware name: BCM2835
   Workqueue: events_highpri bh_work [wfx]
   [<c0212c8c>] (unwind_backtrace) from [<c020d49c>] (show_stack+0x20/0x24)
   [<c020d49c>] (show_stack) from [<c0976220>] (dump_stack+0xd4/0x118)
   [<c0976220>] (dump_stack) from [<c0222270>] (__warn+0x104/0x11c)
   [<c0222270>] (__warn) from [<c02222e0>] (warn_slowpath_fmt+0x58/0x74)
   [<c02222e0>] (warn_slowpath_fmt) from [<bf497b48>] (wfx_skb_dtor+0x1a4/0x1d4 [wfx])
   [<bf497b48>] (wfx_skb_dtor [wfx]) from [<bf4988b4>] (wfx_tx_confirm_cb+0x198/0x2f0 [wfx])
   [<bf4988b4>] (wfx_tx_confirm_cb [wfx]) from [<bf49d054>] (hif_tx_confirm+0x50/0x70 [wfx])
   [<bf49d054>] (hif_tx_confirm [wfx]) from [<bf49d42c>] (wfx_handle_rx+0x128/0x22c [wfx])
   [<bf49d42c>] (wfx_handle_rx [wfx]) from [<bf4953cc>] (bh_work+0x3cc/0x964 [wfx])
   [<bf4953cc>] (bh_work [wfx]) from [<c023dab8>] (process_one_work+0x170/0x458)
   [<c023dab8>] (process_one_work) from [<c023ddfc>] (worker_thread+0x5c/0x5a4)
   [<c023ddfc>] (worker_thread) from [<c02440e8>] (kthread+0x138/0x168)
   [<c02440e8>] (kthread) from [<c02010ac>] (ret_from_fork+0x14/0x28)
   Exception stack(0xee199fb0 to 0xee199ff8)
   9fa0:                                     00000000 00000000 00000000 00000000
   9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
   9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
   ---[ end trace 64b9e754e12ef7de ]---

This patch fix this race between the station creation and the Tx data.

Fixes: 7d2d2bfdeb82 ("staging: wfx: relocate "buffered" information to sta_priv")
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200427134031.323403-11-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>