mac80211: call bss_info_change only once upon disassociation

This patch removes call of ieee80211_bss_info_change_notify from within
ieee80211_reset_erp_info. This allows gathering all bss info changes
into one call to the driver in the disassociation flow.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>