xfs: remove experimental tag for reverse mapping

Reverse mapping has had a while to soak, so remove the experimental tag.
Now that we've landed space metadata cross-referencing in scrub, the
feature actually has a purpose.

Reject rmap filesystems with an rt device until the code to support it
is actually implemented.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>

fs/xfs/xfs_super.c

@@ -1691,15 +1691,11 @@ xfs_fs_fill_super(
 		goto out_filestream_unmount;
 	}
 
-	if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
-		if (mp->m_sb.sb_rblocks) {
-			xfs_alert(mp,
-	"EXPERIMENTAL reverse mapping btree not compatible with realtime device!");
-			error = -EINVAL;
-			goto out_filestream_unmount;
-		}
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb) && mp->m_sb.sb_rblocks) {
 		xfs_alert(mp,
-	"EXPERIMENTAL reverse mapping btree feature enabled. Use at your own risk!");
+	"reverse mapping btree not compatible with realtime device!");
+		error = -EINVAL;
+		goto out_filestream_unmount;
 	}
 
 	error = xfs_mountfs(mp);