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/astro_mcf5373l_defconfig b/configs/astro_mcf5373l_defconfig
index 1e3708f..011dc36 100644
--- a/configs/astro_mcf5373l_defconfig
+++ b/configs/astro_mcf5373l_defconfig
@@ -1,4 +1,5 @@
 CONFIG_M68K=y
+CONFIG_SYS_TEXT_BASE=0x00000000
 CONFIG_TARGET_ASTRO_MCF5373L=y
 CONFIG_BOOTDELAY=1
 CONFIG_USE_BOOTARGS=y