fs/btrfs: Fix warning in btrfs_check_super()

We specifically say that the last arg is u32, so use %lu.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 706286e..2529c2b 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -147,7 +147,7 @@
 
 	if (sb->sys_chunk_array_size < sizeof(struct btrfs_key) +
 	    sizeof(struct btrfs_chunk)) {
-		printf("%s: system chunk array too small %u < %u\n", __func__,
+		printf("%s: system chunk array too small %u < %lu\n", __func__,
 		       sb->sys_chunk_array_size, (u32) sizeof(struct btrfs_key)
 		       + sizeof(struct btrfs_chunk));
 		ret = -1;