zd1211rw: Remove in_atomic() usage.

The usage of in_atomic() in driver code is deprecated as it can not
always detect all states where it is not allowed to sleep.

All callers are in premptible thread context and all functions invoke core
functions which have checks for invalid calling contexts already.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ulrich Kunitz <kune@deine-taler.de>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201101211536.2966644-7-bigeasy@linutronix.de