arm64: dts: freescale: imx8qxp: Remove unnecessary clock related entries

XTAL clocks are not exposed by SCU to OS via OS<->SCU communication protocol,
so remove unnecessary entries.

Signed-off-by: Viorel Suman <viorel.suman@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>