ABI: o2cb: add an obsolete file for /sys/o2cb

This was renamed to /sys/fs/o2cb. Mark the old name as
obsolete.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/25210a6af51b65808e3f102f9f08c3f90b763801.1632750608.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/obsolete/o2cb

+What:		/sys/o2cb
+Date:		Dec 2005
+KernelVersion:	2.6.16
+Contact:	ocfs2-devel@oss.oracle.com
+Description:	Ocfs2-tools looks at 'interface-revision' for versioning
+		information. Each logmask/ file controls a set of debug prints
+		and can be written into with the strings "allow", "deny", or
+		"off". Reading the file returns the current state.
+		Was renamed to /sys/fs/u2cb/
+Users:		ocfs2-tools. It's sufficient to mail proposed changes to
+		ocfs2-devel@oss.oracle.com.

Documentation/ABI/stable/o2cb

-What:		/sys/fs/o2cb/ (was /sys/o2cb)
+What:		/sys/fs/o2cb/
 Date:		Dec 2005
 KernelVersion:	2.6.16
 Contact:	ocfs2-devel@oss.oracle.com