mac80211: fix IE buffer len

Remove size of SSID IE from the IE buffer in scan and
sched scan, since this IE isn't added to this buffer.

Reviewed-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: David Spinadel <david.spinadel@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>