dt-bindings: phy: qmp: Add output-clock-names

The PHY outputs a clock that will act as the parent for
the PHY's pipe clock. Add the name of this clock to the
lane's DT node.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Varadarajan Narayanan <varada@codeaurora.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>