xfs: correct the narrative around misaligned rtinherit/extszinherit dirs

While auditing the realtime growfs code, I realized that the GROWFSRT
ioctl (and by extension xfs_growfs) has always allowed sysadmins to
change the realtime extent size when adding a realtime section to the
filesystem.  Since we also have always allowed sysadmins to set
RTINHERIT and EXTSZINHERIT on directories even if there is no realtime
device, this invalidates the premise laid out in the comments added in
commit 603f000b.

In other words, this is not a case of inadequate metadata validation.
This is a case of nearly forgotten (and apparently untested) but
supported functionality.  Update the comments to reflect what we've
learned, and remove the log message about correcting the misalignment.

Fixes: 603f000b ("xfs: validate extsz hints against rt extent size when rtinherit is set")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>