ARM: dts: imx6qdl-tx6: Drop some duplicated properties

clocks and clock-names are already present in imx6qdl.dtsi since commit
f3e7dae3 ("ARM: dts: imx6qdl: add enet_out clk support"). The change
to imx6qdl.dtsi was explicitly done to avoid this construct in this
file, so benefit from the change and drop these properties.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>