[media] s5p-mfc: Staticize symbols in s5p_mfc_opr_v5.c

Some symbols are used only in this file. Make them static.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>