[media] v4l: Documentation: change path of video drivers

due to structure change for video drivers, change the
description with correct path.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>