xfs: RT bitmap and summary buffers are not typed

xfs: RT bitmap and summary buffers are not typed

Source kernel commit f67ca6eca89cddd355c83639a90109e245f9d5a7

When logging buffers, we attach a type to them that follows the
buffer all the way into the log and is used to identify the buffer
contents in log recovery. Both the realtime summary buffers and the
bitmap buffers do not have types defined or set, so when we try to
log them we see assert failure:

XFS: Assertion failed: (bip->bli_flags & XFS_BLI_STALE) || (xfs_blft_from_flags(&bip->__bli_format) > XFS_BLFT_UNKNOWN_BUF && xfs_blft_from_flags(&bip->__bli_format) < XFS_BLFT_MAX_BUF), file: fs/xfs/xfs_buf_item.c, line: 294

Fix this by adding buffer log format types for these buffers, and
add identification support into log recovery for them. Only build the log
recovery support if CONFIG_XFS_RT=y - we can't get into log recovery for real
time filesystems if support is not built into the kernel, and this avoids
potential build problems.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>