sandbox: drop CONFIG_SYS_RELOC_GD_ENV_ADDR
As we discussed in [1], this option is not needed for sandbox build.
[1] https://lists.denx.de/pipermail/u-boot/2020-February/400182.html
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>