[media] s5p-jpeg: Make s5p_jpeg_g_selection function static

Makes the function s5p_jpeg_g_selection static (detected by sparse).

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