[POWERPC] 4xx: Fix offset value on Warp board

While merging, I found a small bug that I forgot to send. I add an
offset to a value twice.
Signed-off-by: NSean MacLennan <smaclennan@pikatech.com>
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/platforms/44x/warp.c

@@ -137,7 +137,7 @@ static int __init pika_dtm_start(void)
 	}
 	of_node_put(np);
 
-	fpga = ioremap(res.start + 0x20, 4);
+	fpga = ioremap(res.start, 0x24);
 	if (fpga == NULL)
 		return -ENOENT;