arm: dts: sync dts for Allwinner H6

Sync Kernel DTS for Allwinner H6 boards.

Drop /omit-if-no-ref/ keyword as it's not supported by U-boot.

commit <d45331b00ddb> Linux 5.3-rc4

Signed-off-by: Clément Péron <peron.clem@gmail.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>