dt-bindings: phy: cadence-torrent: Add binding to specify SSC mode

Add binding to specify Spread Spectrum Clocking mode used.

Signed-off-by: Swapnil Jakhade <sjakhade@cadence.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1600280911-9214-7-git-send-email-sjakhade@cadence.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>