configs: smdkv310: get rid of unused EXYNOS4_DEFAULT_UART_OFFSET

Unused.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>