mac80211_hwsim: use GFP_ATOMIC under spin lock

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

Fixes: 5d44fe7c

 ("mac80211_hwsim: add frame transmission support over virtio")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200422020154.112088-1-weiyongjun1@huawei.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>