media: s5p-mfc: Use display delay and display enable std controls

Use the standard display_delay and display_delay_enable controls,
the legacy private MFC controls are kept for backward compatibility.

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>