ARM: dts: imx7d: move CPU operating points to imx7d.dtsi

Only i.MX 7Dual SoC supports CPU frequencies of up to 1GHz. The i.MX
7Solo can run with up to 800MHz and does so without making use of DVFS
usually. While the device tree clearly specified a too fast operating
point for i.MX 7Solo, the kernel did not used it in practise so far
because the CPUfreq driver does not get loaded on i.MX 7Solo devices
(since the fsl,imx7s compatible string is not in the list of devices
making use of the cpufreq-dt driver...).

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>