wifi: mac80211: Recalc offload when monitor stop

When a monitor interface is started, ieee80211_recalc_offload() is
called and 802.11 encapsulation offloading support get disabled so
monitor interface could get native wifi frames directly. But when
this interface is stopped there is no need to keep the 802.11
encpasulation offloading off.

This call ieee80211_recalc_offload() when monitor interface is stopped
so 802.11 encapsulation offloading gets re-activated if possible.

Fixes: 6aea26ce

 ("mac80211: rework tx encapsulation offload API")
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Link: https://msgid.link/840baab454f83718e6e16fd836ac597d924e85b9.1716048326.git.repk@triplefau.lt
Signed-off-by: Johannes Berg <johannes.berg@intel.com>