arm64: dts: imx8mp: drop gpcv2 vpu power-domains and clocks

The GPCv2 G1, G2 and VC8000E power-domain don't need to reference the
VPUMIX power-domain nor their module clocks since the power and reset
handling is done by the VPUMIX blkctrl driver.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Adam Ford <aford173@gmail.com>
LGTM: Peng Fan <peng.fan@nxp.com>
Tested-by: Adam Ford <aford173@gmail.com> #imx8mp-beacon-kit
Signed-off-by: Shawn Guo <shawnguo@kernel.org>