mpc83xx: implement board_add_ram_info

add board_add_ram_info, to make memory diagnostic output more
consistent. u-boot banner output now looks like:

DRAM:  256 MB (DDR1, 64-bit, ECC on)

and for boards with SDRAM on the local bus, a line such as this is
added:

SDRAM: 64 MB (local bus)

also replaced some magic numbers with their equivalent define names.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/include/configs/MPC8313ERDB.h b/include/configs/MPC8313ERDB.h
index e2ec0bc..db79ce2 100644
--- a/include/configs/MPC8313ERDB.h
+++ b/include/configs/MPC8313ERDB.h
@@ -113,12 +113,12 @@
 				/* 0x03200064 */
 #if defined(CONFIG_DDR_2T_TIMING)
 #define CFG_SDRAM_CFG		( SDRAM_CFG_SREN \
-				| 3 << SDRAM_CFG_SDRAM_TYPE_SHIFT \
+				| SDRAM_CFG_SDRAM_TYPE_DDR2 \
 				| SDRAM_CFG_2T_EN \
 				| SDRAM_CFG_DBW_32 )
 #else
 #define CFG_SDRAM_CFG		( SDRAM_CFG_SREN \
-				| 3 << SDRAM_CFG_SDRAM_TYPE_SHIFT \
+				| SDRAM_CFG_SDRAM_TYPE_DDR2 \
 				| SDRAM_CFG_32_BE )
 				/* 0x43080000 */
 #endif