arm64: dts: ls1046a: make dma-coherent global to the SoC

These SoCs are really completely dma coherent in their entirety so add
the dma-coherent property at the soc level in the device tree and drop
the instances where it's specifically added to a few select devices.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>