[media] v4l: tvp5150: Compile tvp5150_link_setup out if !CONFIG_MEDIA_CONTROLLER

The function is only referenced as a handler in the tvp5150_sd_media_ops
structure, which is only used when CONFIG_MEDIA_CONTROLLER is set. Don't
define the function and the structure when the configuration option is
unset to avoid an unused function warning.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>