uboot-imx

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: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Stefan Roese <sr@denx.de>