media: davinci: make function arguments const

Make the function arguments of functions vpfe_{register/unregister}_ccdc_device
const as the pointer dev does not modify the fields of the structure
it points to. Also, declare the variable ccdc_dev const as it points to the
same structure as dev but it does not modify the fields as well.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>