iwlwifi: mvm: fix bug in scan ssid

commit fe04e837 upstream.

Increment index in each iteration. Without this increment we are
overriding the added SSIDs and we will send only the last SSId
and (n_ssids - 1) broadcast probes.

Signed-off-by: David Spinadel <david.spinadel@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>