powerpc/8xxx: Fix bug in memctrl interleaving & bank interleaving on cs0~cs4

Verified on MPC8641HPCN with four DDR2 dimms. Each dimm has dual
rank with 512MB each rank.

Also check dimm size and rank size for memory controller interleaving

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/include/configs/MPC8641HPCN.h b/include/configs/MPC8641HPCN.h
index 0d1f779..974cb6b 100644
--- a/include/configs/MPC8641HPCN.h
+++ b/include/configs/MPC8641HPCN.h
@@ -122,6 +122,8 @@
 #define CONFIG_SYS_CCSRBAR_PHYS		CONFIG_SYS_CCSRBAR_PHYS_LOW
 #endif
 
+#define CONFIG_HWCONFIG	/* use hwconfig to control memory interleaving */
+
 /*
  * DDR Setup
  */