nl80211: Fix max_remain_on_chan capability reading

nl80211: Fix max_remain_on_chan capability reading

In case that NL80211_PROTOCOL_FEATURE_SPLIT_WIPHY_DUMP is supported,
wiphy_info_handler() is called several times, where
NL80211_ATTR_MAX_REMAIN_ON_CHANNEL_DURATION is present only in one
of these calls. Thus capa->max_remain_on_chan is overridden in
all other calls.

Fix it so the default value is set only after all the wiphy info was
received.

Signed-hostap: Ilan Peer <ilan.peer@intel.com>