staging: vt6656: rxtx.c s:_uGetDataDuration simplify structure.

A value is only returned when bNeedAck is true.

Only when byDurType == DATADUR_B is different.

Remove switch statement and simplify with if structure.

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