UBI: add layout volume information

Add more information about layout volume to make userspace tools
use the macros instead of constants. Also rename UBI_LAYOUT_VOL_ID
to make it consistent with other macros.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 1f951e3..1f7375e 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -78,7 +78,7 @@
  */
 static int ubi_get_compat(const struct ubi_device *ubi, int vol_id)
 {
-	if (vol_id == UBI_LAYOUT_VOL_ID)
+	if (vol_id == UBI_LAYOUT_VOLUME_ID)
 		return UBI_LAYOUT_VOLUME_COMPAT;
 	return 0;
 }