staging: vt6656: implement get_stats ieee80211_low_level_stats

The driver already report low_level_stats via vnt_interrupt_data.

Allow mac80211 to collect them via vnt_get_stats

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>