greybus: camera: Don't configure CSI TX in test only mode

When the GB_CAMERA_CONFIGURE_STREAMS_TEST_ONLY flag is set by the caller
the configure streams operation should only test the requested settings
without modifying the hardware state. This applies for both the module,
the UniPro links power modes and the AP bridge settings. Return early
when the flag is set to avoid modifying the AP bridge CSI TX settings.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Gjorgji Rosikopulos <grosikopulos@mm-sol.com>
Tested-by: Jacopo Mondi <jacopo.mondi@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>