Btrfs: Introduce BTRFS_BLOCK_GROUP_RAID56_MASK to check raid56 simply

So we can check raid56 with:
 (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
instead of long:
 (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6))

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0b4683f..2ecdac0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1020,6 +1020,9 @@
 					 BTRFS_BLOCK_GROUP_RAID6 |   \
 					 BTRFS_BLOCK_GROUP_DUP |     \
 					 BTRFS_BLOCK_GROUP_RAID10)
+#define BTRFS_BLOCK_GROUP_RAID56_MASK	(BTRFS_BLOCK_GROUP_RAID5 |   \
+					 BTRFS_BLOCK_GROUP_RAID6)
+
 /*
  * We need a bit for restriper to be able to tell when chunks of type
  * SINGLE are available.  This "extended" profile format is used in