V4L/DVB (13656): tw9910: tw9910_set_hsync clean up

tw9910_set_hsync should use tw9910_mask_set to set bits 2-0

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>