media: bttv: copy vid fmt/width/height from fh

In preparation for the vb2 conversion, copy the video format, width and
height fields from struct bttv_fh and add them to the main struct bttv.
Use these fields from struct bttv wherever they will be needed after the
vb2 conversion which stops using separate bttv file handles altogether. To
avoid changing more code than necessary, just leave the video format,
width and height fields in separate file handles wherever the code will be
subsequently removed by vb2.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>