media: vimc: expand the names of vimc entity types

When introducing the lens controller, it became apparent that the vimc
entity type names were hard to understand, e.g. vimc_len_type refers to the
lens. The names of the vimc entity types have been expanded to make the
code easier to understand. 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>