media: s5p-mfc: constify s5p_mfc_hw_cmds structures

Static "s5p_mfc_hw_cmds" structures are not modified by the driver, so
they can be made const for code safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Aakarsh Jain <aakarsh.jain@samsung.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

media: platform: rename s5p-mfc/ to samsung/s5p-mfc/

As the end goal is to have platform drivers split by vendor,
rename s5p-mfc/ to samsung/s5p-mfc/.

Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>