[media] s5p-fimc: Minor cleanups

Tidy up the variant and driver data handling. Remove the 'samsung_'
prefix from some data structures since it doesn't really carry any
useful information and makes the names unnecessarily long.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>