arm64: dts: imx8mm-venice-gw73xx: remove compatible in overlay file

Remove compatible string in overlay file to fix below warning:
'gw,imx8mm-gw73xx-0x' is not one of ['fsl,ls1043a-rdb', 'fsl,ls1043a-qds']

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>