[media] davinci_vpfe: fix copy-paste errors in several comments

This removes some incorrect dv_preset references left over from copy-and-paste
errors.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>