docs-rst: don't ignore internal functions for jbd2 docs

Those functions are currently ignored, causing references at
the documentation to be lost. Don't ignore it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
index 148becd..256e10e 100644
--- a/Documentation/filesystems/index.rst
+++ b/Documentation/filesystems/index.rst
@@ -287,7 +287,6 @@
 ~~~~~~~~~~~~~~~~~~
 
 .. kernel-doc:: fs/jbd2/transaction.c
-   :export:
 
 See also
 --------