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/boston64r2_defconfig b/configs/boston64r2_defconfig
index 0e97dcf..ea0e2a1 100644
--- a/configs/boston64r2_defconfig
+++ b/configs/boston64r2_defconfig
@@ -1,4 +1,5 @@
 CONFIG_MIPS=y
+CONFIG_SYS_TEXT_BASE=0xFFFFFFFF9FC00000
 CONFIG_TARGET_BOSTON=y
 CONFIG_CPU_MIPS64_R2=y
 # CONFIG_MIPS_BOOT_CMDLINE_LEGACY is not set