staging: brcm80211: bug fix for n_ssids usage and update drv_info

-update drv_info so it's visible in "ethtool -i" output
-remove n_ssids usage. Fixes nullptr deref bug seen before.

Signed-off-by: Grant Grundler <grundler@chromium.org>
Acked-by: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>