staging: vt6656: s_vFillCTSHead join structures of vnt_cts* to union vnt_tx_data_head

Only one of vnt_rts*/vnt_cts* structures are accessed at any one time.

structures vnt_cts and vnt_cts_fb are members of union vnt_tx_data_head.

Create pointer union head and point structures to the correct member.

Point the union to pvCTS.

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