V4L/DVB (13664): tw9910: use V4L2_FIELD_INTERLACED_BT

tw9910 output is interlaced and its correct order is Bottom - Top

Signed-off-by: Kuninori Morimoto <morimoto.kuninori@renesas.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>