staging: vt6656: rxtx.c s_vGenerateTxParameter replace pTxBufHead void pointer.

with struct vnt_tx_buffer and attach vnt_tx_fifo_head to pTX_Buffer structure.

The the calling pbyTxBufferAddr points to the same address as
vnt_tx_buffer->fifo_head and is still in use.

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