orinoco: Annotate ezusb_docmd_wait()

All invocations of ezusb_docmd_wait() happen via ->cmd_wait(). This
callback is always invoked under the orinoco_lock() which disables BH.

Use ezusb_req_ctx_wait_poll() for ezusb_docmd_wait() because it must not
sleep.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201113212252.2243570-10-bigeasy@linutronix.de