Port of Linux commit 66de33f

    The num-lanes is optional since it is not needed on some platforms
    that bring up the link in firmware.

    The link programming is based on the num-lanes properties (which is
    optional); if it is not present code must return instead of fiddling
    with the lanes value to print an error message.

    Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
    Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Reviewed-by: Andrew Murray <andrew.murray@arm.com>

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>