x86, iosf: Make IOSF driver modular and usable by more drivers

x86, iosf: Make IOSF driver modular and usable by more drivers

Currently drivers that run on non-IOSF systems (Core/Xeon) can't use the IOSF
driver on SOC's without selecting it which forces an unnecessary and limiting
dependency. Provides dummy functions to allow these modules to conditionally
use the driver on IOSF equipped platforms without impacting their ability to
compile and load on non-IOSF platforms. Build default m to ensure availability
on x86 SOC's.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1399668248-24199-2-git-send-email-david.e.box@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>