docs: filesystems: convert dnotify.txt to ReST

- Add a SPDX header;
- Add a document title;
- Some whitespace fixes and new line breaks;
- Add table markups;
- Add it to filesystems/index.rst

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Acked-by: Jan Kara <[e-mail]>
Link: https://lore.kernel.org/r/b39d64[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/filesystems/dnotify.txt Documentation/filesystems/dnotify.rst

···
-		Linux Directory Notification
-		============================
+.. SPDX-License-Identifier: GPL-2.0
+
+============================
+Linux Directory Notification
+============================
 
 	   Stephen Rothwell <[e-mail]>
 
···
 The application decides which "events" it wants to be notified about.
 The currently defined events are:
 
+	=========	=====================================================
 	DN_ACCESS	A file in the directory was accessed (read)
 	DN_MODIFY	A file in the directory was modified (write,truncate)
 	DN_CREATE	A file was created in the directory
···
 	DN_RENAME	A file in the directory was renamed
 	DN_ATTRIB	A file in the directory had its attributes
 			changed (chmod,chown)
+	=========	=====================================================
 
 Usually, the application must reregister after each notification, but
 if DN_MULTISHOT is or'ed with the event mask, then the registration will
···
 is often blocked, so it is better to use (at least) SIGRTMIN + 1.
 
 Implementation expectations (features and bugs :-))
----------------------------
+---------------------------------------------------
 
 The notification should work for any local access to files even if the
 actual file system is on a remote server.  This implies that remote

Documentation/filesystems/index.rst

···
    locking
    directory-locking
    devpts
+   dnotify
 
    automount-support
 

MAINTAINERS

···
 R:	Amir Goldstein <[e-mail]>
 L:	[e-mail]
 S:	Maintained
-F:	Documentation/filesystems/dnotify.txt
+F:	Documentation/filesystems/dnotify.rst
 F:	fs/notify/dnotify/
 F:	include/linux/dnotify.h