docs: filesystems: fix renamed references

Some filesystem references got broken by a previous patch
series I submitted. Address those.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: David Sterba <dsterba@suse.com> # fs/affs/Kconfig
Link: https://lore.kernel.org/r/57318c53008dbda7f6f4a5a9e5787f4d37e8565a.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index 3fb1f55..1ad211d 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -8,7 +8,7 @@
 	  If you say Y here, you will get an experimental Andrew File System
 	  driver. It currently only supports unsecured read-only AFS access.
 
-	  See <file:Documentation/filesystems/afs.txt> for more information.
+	  See <file:Documentation/filesystems/afs.rst> for more information.
 
 	  If unsure, say N.
 
@@ -18,7 +18,7 @@
 	help
 	  Say Y here to make runtime controllable debugging messages appear.
 
-	  See <file:Documentation/filesystems/afs.txt> for more information.
+	  See <file:Documentation/filesystems/afs.rst> for more information.
 
 	  If unsure, say N.
 
@@ -37,6 +37,6 @@
 	  the dmesg log if the server rotation algorithm fails to successfully
 	  contact a server.
 
-	  See <file:Documentation/filesystems/afs.txt> for more information.
+	  See <file:Documentation/filesystems/afs.rst> for more information.
 
 	  If unsure, say N.