iwlwifi: mvm: remove extra SSID from probe request

Bits 1-21 in this channel type attributes are indication for which
SSID is going to be sent on this channel. Since the first SSID is
sent implicitly in the probe request, we don't need to toggle its
bit here.

Signed-off-by: David Spinadel <david.spinadel@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>