[media] vivid: fix try_fmt behavior

[media] vivid: fix try_fmt behavior

vivid_try_fmt_vid_cap() called tpg_calc_line_width to calculate the sizeimage
value, but that tpg function uses the current format, not the proposed (tried)
format.

Rewrote this code to calculate this correctly.

The vivid_try_fmt_vid_out() code was completely wrong w.r.t. sizeimage, and
neither did it take the vdownsampling[] factors into account.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Vincent Abriou <vincent.abriou@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>