powerpc: yucca: drop redundant CONFIG_SYS_TEXT_BASE from config.mk
The include/configs/yucca.h already has the same define:
#define CONFIG_SYS_TEXT_BASE 0xfffb0000
Remove the redundant one from board/amcc/yucca/config.mk.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Stefan Roese <sr@denx.de>