powerpc: mpc5xxx: remove redundant CONFIG_MPC5xxx definition

We do not have to define CONFIG_MPC5xxx in board config headers
(and start.S) because it is defined in arch/powerpc/cpu/mpc5xxx/config.mk.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/include/configs/IceCube.h b/include/configs/IceCube.h
index 52368f8..1861aa8 100644
--- a/include/configs/IceCube.h
+++ b/include/configs/IceCube.h
@@ -13,8 +13,7 @@
  * (easy to change)
  */
 
-#define CONFIG_MPC5xxx		1	/* This is an MPC5xxx CPU */
-#define CONFIG_MPC5200		1	/* (more precisely a MPC5200 CPU) */
+#define CONFIG_MPC5200		1	/* This is a MPC5200 CPU */
 #define CONFIG_ICECUBE		1	/* ... on IceCube board */
 
 /*