staging: vt6656: Move key_buffer inside vnt_fill_txkey.

Use vnt_tx_fifo_head to point directly at tx_key removing key_buffer.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/3631f327-1386-90a2-ba9a-bb62617f3c66@gmail.com


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