mac80211_hwsim: fix typo in kernel-doc

There's a stray _ in the kernel doc, remove it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200924192511.6a344ebd8d65.Ie95a47db5887b8d2faa8ca2df474a955a376c4c4@changeid


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