arm: rmobile: koelsch: Add CONFIG_SCIF_USE_EXT_CLK

SCIF of koelsch use external clock mode.
This enables external clock mode on koelsch board.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
diff --git a/include/configs/koelsch.h b/include/configs/koelsch.h
index 21667d1..e015e90 100644
--- a/include/configs/koelsch.h
+++ b/include/configs/koelsch.h
@@ -89,6 +89,7 @@
 /* SCIF */
 #define CONFIG_SCIF_CONSOLE
 #define CONFIG_CONS_SCIF0
+#define CONFIG_SCIF_USE_EXT_CLK
 #undef	CONFIG_SYS_CONSOLE_INFO_QUIET
 #undef	CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
 #undef	CONFIG_SYS_CONSOLE_ENV_OVERWRITE