Bluetooth: btsdio: fix use after free bug in btsdio_remove due to unfinished work

In btsdio_probe, &data->work was bound with btsdio_work.In
btsdio_send_frame, it was started by schedule_work.

If we call btsdio_remove with an unfinished job, there may
be a race condition and cause UAF bug on hdev.

Fixes: ddbaf13e

 ("[Bluetooth] Add generic driver for Bluetooth SDIO devices")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>