LF-168: arm64: dts: imx8qm: modify GPU frequency according to 8QM spec

LF-168: arm64: dts: imx8qm: modify GPU frequency according to 8QM spec

modify GPU core clock to 800000 and GPU shader clock to 1000000.

As per commit 30d9947ad71007("LF-168: arm64: dts: imx8qm: add frequency
operating-points to enable GPU governor") the operating-points node use
the wrong GPU core clock and shader clock.

So, modify GPU frequency according to 8QM spec

Fixes:30d9947ad71007("LF-168: arm64: dts: imx8qm: add frequency
operating-points to enable GPU governor")

Signed-off-by: Minjie Zhuang <minjie.zhuang@nxp.com>