greybus: camera: Rename clock_mode to flags

Rename the 'clock_mode' parameter to a more generic 'flags' in the csi
bus configuration structure.
Define flags value for continuous clock mode.

Signed-off-by: Jacopo Mondi <jacopo.mondi@linaro.org>
Acked-by: Laurent Pinchart <laurent.pinchart@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>