[media] [REVIEW] em28xx: fix bytesperline calculation in TRY_FMT

The bytesperline calculation was incorrect: it used the old width instead of
the provided width. Fixed.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>