arm64: allwinner: Add aw_syscon driver to GENERIC

Recent DTS use the syscon for the emac controller.
We support this but since U-Boot is still using old DTS it was never
needed for us to add this support, but this is a problem when using upstream
recent DTS and will be when U-Boot will catch up.

While here add a new compatible to the aw_syscon driver as Linux changed it ...