sgi-ioc4.txt: standardize document format

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx.

In this case, just adding a title is enough.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/sgi-ioc4.txt

+====================================
+SGI IOC4 PCI (multi function) device
+====================================
+
 The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
 it are in order.