kbuild: drop workaround for old style CONFIG_SYS_TEXT_BASE defines

Now, there is no board defining CONFIG_SYS_TEXT_BASE by its config.mk,
so this workaround is no longer needed.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NStefan Roese <sr@denx.de>

Makefile

@@ -591,12 +591,6 @@ endif
 # Prohibit date/time macros, which would make the build non-deterministic
 KBUILD_CFLAGS   += $(call cc-option,-Werror=date-time)
 
-ifneq ($(CONFIG_SYS_TEXT_BASE),)
-KBUILD_CPPFLAGS += -DCONFIG_SYS_TEXT_BASE=$(CONFIG_SYS_TEXT_BASE)
-endif
-
-export CONFIG_SYS_TEXT_BASE
-
 include scripts/Makefile.extrawarn
 
 # Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments