ieee80211: Fix incorrect mask for default PE duration

Fixes bitmask for HE opration's default PE duration.

Fixes: daa5b835 ("mac80211: update HE operation fields to D3.0")
Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Link: https://lore.kernel.org/r/20200506102430.5153-1-pradeepc@codeaurora.org


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