arm: rmobile: koelsch: Enable optimization of thumb

This adds CONFIG_SYS_THUMB_BUILD to config, in order to enable optimization
of thumb.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>

include/configs/koelsch.h

@@ -35,6 +35,7 @@
 #define CONFIG_CMD_SF
 #define CONFIG_CMD_SPI
 #define CONFIG_SYS_TEXT_BASE	0xE6304000
+#define CONFIG_SYS_THUMB_BUILD
 
 #define	CONFIG_CMDLINE_TAG
 #define	CONFIG_SETUP_MEMORY_TAGS