x86/iosf: Add debugfs support

Allows access to the iosf sideband through debugfs.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1409175640-32426-3-git-send-email-david.e.box@linux.intel.com


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>