dt-bindings: clock: imx6qdl: Add clock defines

Add imx6qdl clock header defines support from Linux.

"clk: imx: Add clock support for imx6qp"
(sha1: ee36027427c769b0b9e5e205fe43aced93d6aa66)

Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>