configs: Migrate CONFIG_SYS_TEXT_BASE

On the NIOS2 and Xtensa architectures, we do not have
CONFIG_SYS_TEXT_BASE set.  This is a strict migration of the current
values into the defconfig and removing them from the headers.

I did not attempt to add more default values in and for now will leave
that to maintainers.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 3acf908..c0f4c0a 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -1,3 +1,4 @@
+CONFIG_SYS_TEXT_BASE=0
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_DEFAULT_DEVICE_TREE="sandbox"
 CONFIG_DISTRO_DEFAULTS=y