staging: vt6655: mac80211 conversion: s_uFillDataHead add power saving poll

Replace variable wCurrentRate with is_pspoll.

add current_aid to structure vnt_private which is to be used by
mac80211 operations.

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