arm: mvebu: db-mv784mp-gp: Fix ECC I2C address

The macro to select the I2C address for ECC bus-width detection
was defined incorrectly for the Marvell DB-MV784MP-GP board. This
patch changes the macro to the correct value to fix this issue.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/ddr/mvebu/ddr3_axp.h b/drivers/ddr/mvebu/ddr3_axp.h
index bf65f6b..d9e33f7 100644
--- a/drivers/ddr/mvebu/ddr3_axp.h
+++ b/drivers/ddr/mvebu/ddr3_axp.h
@@ -35,7 +35,7 @@
 
 #define ECC_SUPPORT
 #define NEW_FABRIC_TWSI_ADDR		0x4E
-#ifdef DB_784MP_GP
+#ifdef CONFIG_DB_784MP_GP
 #define BUS_WIDTH_ECC_TWSI_ADDR		0x4E
 #else
 #define BUS_WIDTH_ECC_TWSI_ADDR		0x4F