rockchip: make_fit_atf: fix warning unit_address_vs_reg

rockchip: make_fit_atf: fix warning unit_address_vs_reg

Patch fix warning:
/builddir/BUILD/u-boot-2018.05-rc2/"arch/arm/mach-rockchip/make_fit_atf.py" \
arch/arm/dts/rk3399-firefly.dtb > u-boot.its
  ./tools/mkimage  -f u-boot.its -E u-boot.itb >/dev/null  && cat
/dev/null
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node /images/uboot@1
has a unit name, but no reg property
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node /images/atf@1 has
a unit name, but no reg property
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node /images/atf@2 has
a unit name, but no reg property
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node /images/atf@3 has
a unit name, but no reg property
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node /images/fdt@1 has
a unit name, but no reg property
u-boot.itb.tmp: Warning (unit_address_vs_reg): Node
/configurations/config@1 has a unit name, but no reg property
make[1]: Leaving directory
'/builddir/BUILD/u-boot-2018.05-rc2/builds/firefly-rk3399'

Reported-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>