staging: wfx: remove useless call to wfx_tx_flush()

wfx_do_join() calls wfx_tx_lock_flush() ate beginning of the function.
Therefore, the subsequent call to wfx_tx_flush() is useless.
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200410133239.438347-8-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/sta.c

@@ -493,8 +493,6 @@ static void wfx_do_join(struct wfx_vif *wvif)
 	}
 	rcu_read_unlock();
 
-	wfx_tx_flush(wvif->wdev);
-
 	if (wvif_count(wvif->wdev) <= 1)
 		hif_set_block_ack_policy(wvif, 0xFF, 0xFF);