sunxi: arm64: correct usage of DT node address in FIT generation

The DT spec demands a unit-address in a node name to match the "reg"
property in that node. Newer dtc versions will throw warnings if this is
not the case.
Adjust the FIT build script for 64-bit Allwinner boards to remove the
bogus addresses from the node names and avoid the warnings.
This avoids a warning with recent versions of the dtc tool.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>