staging: vt6656: Move vnt_mic_hdr pointers to vnt_fill_txkey

mic_hdr has three possible locations ieee80211_tx_info can controls
these with control.use_cts_prot for rts or cts exchange or otherwise
the rts/data position.

Removing double pointer.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/6420a6ae-82eb-f794-fa7c-bac419222ad6@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>