Disable memory controller before setting first values.

cpu/ppc4xx/sdram.c

@@ -80,6 +80,11 @@ void sdram_init(void)
 		rtr = 0x05f00000;
 	}
 
+	/*
+	 * Disable memory controller.
+	 */
+	mtsdram0(mem_mcopt1, 0x00000000);
+
 	/*
 	 * Set MB0CF for bank 0. (0-128MB) Address Mode 3 since 13x10(4)
 	 */