powerpc: T4240: Remove macro CONFIG_PPC_T4240

Use CONFIG_ARCH_T4240 from Kconfig instead.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/include/configs/T4240RDB.h b/include/configs/T4240RDB.h
index da536f0..6c743e3 100644
--- a/include/configs/T4240RDB.h
+++ b/include/configs/T4240RDB.h
@@ -732,7 +732,7 @@
  * interleaving. It can be cacheline, page, bank, superbank.
  * See doc/README.fsl-ddr for details.
  */
-#ifdef CONFIG_PPC_T4240
+#ifdef CONFIG_ARCH_T4240
 #define CTRL_INTLV_PREFERED 3way_4KB
 #else
 #define CTRL_INTLV_PREFERED cacheline