Fix the chapter heading for "X.25 Device Driver Interface" so that it
does not contain a trailing '-' character, which makes Sphinx
omit this heading from the contents.

Reverse the order of the x25.rst and x25-iface.rst files in the index
so that the project introduction (x25.rst) comes first.

Fixes: 883780af ("docs: networking: convert x25-iface.txt to ReST")
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Martin Schiller <ms@dev.tdt.de>
Cc: linux-x25@vger.kernel.org
Reviewed-by: NBagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>