Blackfin: drop CONFIG_SYS_TEXT_BASE from boards

We don't want/use this value for Blackfin boards, so punt it and have the
common code error out when people try to use it.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/config.mk b/arch/blackfin/config.mk
index f4503ea..92520e8 100644
--- a/arch/blackfin/config.mk
+++ b/arch/blackfin/config.mk
@@ -70,3 +70,7 @@
 ifeq ($(wildcard $(TOPDIR)/board/$(BOARD)/u-boot.lds*),)
 LDSCRIPT = $(obj)arch/$(ARCH)/lib/u-boot.lds.S
 endif
+
+ifneq ($(CONFIG_SYS_TEXT_BASE),)
+$(error do not set CONFIG_SYS_TEXT_BASE for Blackfin boards)
+endif