wifi: cfg80211/mac80211: apply HE OBSS PD settings on beacon update

hostapd puts NL80211_ATTR_HE_OBSS_PD into NL80211_CMD_SET_BEACON as well
as NL80211_CMD_START_AP, but cfg80211 parses it only when the AP starts.
A change of the spatial reuse parameters therefore reaches the beacon
but not the driver, and the only way to apply it is to restart the AP,
which disconnects all stations.

Parse the attribute in the AP update path and apply it in
ieee80211_change_beacon() when it differs from the current settings.

Assisted-by: LLM
Signed-off-by: John Macias <dencity7@gmail.com>
Link: https://patch.msgid.link/20261026035803.2630025-1-dencity7@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>