[media] s5p-fimc: Refactor the register interface functions

Simplify the register API and use FIMC_REG_ prefix for all register
definitions for consistency with FIMC-LITE. The unused image effect
defines are removed.

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>