f2fs: fix wrong __is_meta_io() macro

This patch changes codes as below:
- don't use is_read_io() as a condition to judge the meta IO.
- use .is_por to replace .is_meta to indicate IO is from recovery explicitly.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 935ebdb..f42b001 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -66,7 +66,7 @@
 		.old_blkaddr = index,
 		.new_blkaddr = index,
 		.encrypted_page = NULL,
-		.is_meta = is_meta,
+		.is_por = !is_meta,
 	};
 	int err;
 
@@ -189,7 +189,7 @@
 		.op_flags = sync ? (REQ_META | REQ_PRIO) : REQ_RAHEAD,
 		.encrypted_page = NULL,
 		.in_list = false,
-		.is_meta = (type != META_POR),
+		.is_por = (type == META_POR),
 	};
 	struct blk_plug plug;