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.