UBI: Fix size parsing in "ubi create"

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/common/cmd_ubi.c b/common/cmd_ubi.c
index 495d71e..fd33a67 100644
--- a/common/cmd_ubi.c
+++ b/common/cmd_ubi.c
@@ -546,7 +546,7 @@
 		}
 		/* E.g., create volume size */
 		if (argc == 4) {
-			addr = simple_strtoul(argv[3], NULL, 16);
+			size = simple_strtoul(argv[3], NULL, 16);
 			argc--;
 		}
 		/* Use maximum available size */