[media] v4l/s5p-mfc: corrected encoder v4l control definitions

Patch corrects definition of H264 level control and
changes bare numbers to enums in two other cases.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>