UBI: improve internal interfaces

Pass volume description object to the EBA function which makes
more sense, and EBA function do not have to find the volume
description object by volume ID.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/upd.c b/drivers/mtd/ubi/upd.c
index 0efc586..a95dcaa 100644
--- a/drivers/mtd/ubi/upd.c
+++ b/drivers/mtd/ubi/upd.c
@@ -136,7 +136,7 @@
 
 	/* Before updating - wipe out the volume */
 	for (i = 0; i < vol->reserved_pebs; i++) {
-		err = ubi_eba_unmap_leb(ubi, vol_id, i);
+		err = ubi_eba_unmap_leb(ubi, vol, i);
 		if (err)
 			return err;
 	}
@@ -209,8 +209,7 @@
 		if (len != l)
 			dbg_msg("skip last %d bytes (0xFF)", len - l);
 
-		err = ubi_eba_write_leb(ubi, vol_id, lnum, buf, 0, l,
-					UBI_UNKNOWN);
+		err = ubi_eba_write_leb(ubi, vol, lnum, buf, 0, l, UBI_UNKNOWN);
 	} else {
 		/*
 		 * When writing static volume, and this is the last logical
@@ -222,7 +221,7 @@
 		 * contain zeros, not random trash.
 		 */
 		memset(buf + len, 0, vol->usable_leb_size - len);
-		err = ubi_eba_write_leb_st(ubi, vol_id, lnum, buf, len,
+		err = ubi_eba_write_leb_st(ubi, vol, lnum, buf, len,
 					   UBI_UNKNOWN, used_ebs);
 	}