media: v4l2-ioctl: call v4l_pix_format_touch() for TRY_FMT

The function v4l_pix_format_touch() is called for S_FMT to set
v4l2_pix_format fields to default values for a v4l-touch device,
but it wasn't called for TRY_FMT. Add this.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>