mwifiex: add tx info to skb when forming mgmt frame

In function 'mwifiex_write_data_complete' it need tx info to find
the mwifiex_private to updates statistics and wake up tx queues.
Or we may trigger tx queues timeout when transmitting lots of mgmt
frames.

Signed-off-by: Huawei Yang <harvey.huawei.yang@gmail.com>
Signed-off-by: Stone Piao <piaoyun@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>