ARM: dts: s5pv210: correct ethernet unit address in SMDKV210

The SROM bank 5 is at address 0xa8000000, just like the one put in "reg"
property of ethernet node.  Fix the unit address of ethernet node.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200907183313.29234-2-krzk@kernel.org