tegra: Remove unnecessary CONFIG_SYS_NAND_BASE

Now that we are using the new CONFIG_SYS_NAND_SELF_INIT setup, we don't
need CONFIG_SYS_NAND_BASE. Punt it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>