wlcore: compare ssid_len before comparing ssids

When comparing 2 ssids the ssid_len must be taken
into account. Otherwise, a substring will be treated
as equal.

This bug might cause ssids to get scanned as
public ssids (rather than hidden), resulting in
broadcast probe request (instead of ssid-specific
ones)

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>