media: vimc: use data link entities enum to index the ent_config array

Future additions to the ent_config[] could break the association between
the index of the struct vimc_ent_config entries in the ent_config[] array,
and the index defined by the enum proposed in the previous patch. Using
designated initializers solves this by linking the 2 together clearly in
code and prevents the array not reflecting the enum. There is no
functional change intended.

Suggested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Daniel Oakley <daniel.oakley@ideasonboard.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>