x86/platform/intel/iosf: Add debugfs config option for IOSF

Makes the IOSF sideband available through debugfs. Allows
developers to experiment with using the sideband to provide
debug and analytical tools for units on the SoC.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1411017231-20807-4-git-send-email-david.e.box@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>