Btrfs: fix compiler warnings on 32 bit systems

The enospc tracing code added some interesting uses of
u64 pointer casts.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 213ffa8..ee15d88 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -438,7 +438,8 @@
 					  trans->bytes_reserved);
 	if (ret)
 		goto out;
-	trace_btrfs_space_reservation(root->fs_info, "ino_cache", (u64)trans,
+	trace_btrfs_space_reservation(root->fs_info, "ino_cache",
+				      (u64)(unsigned long)trans,
 				      trans->bytes_reserved, 1);
 again:
 	inode = lookup_free_ino_inode(root, path);
@@ -500,7 +501,8 @@
 out_put:
 	iput(inode);
 out_release:
-	trace_btrfs_space_reservation(root->fs_info, "ino_cache", (u64)trans,
+	trace_btrfs_space_reservation(root->fs_info, "ino_cache",
+				      (u64)(unsigned long)trans,
 				      trans->bytes_reserved, 0);
 	btrfs_block_rsv_release(root, trans->block_rsv, trans->bytes_reserved);
 out: