ath11k: use GFP_ATOMIC under spin lock

A spin lock is taken here so we should use GFP_ATOMIC.

Fixes: d5c65159

 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200427092417.56236-1-weiyongjun1@huawei.com