ASoC: Intel: Add Skylake IPC library

This adds base SKL IPC library which uses common SST IPC lib.
Here we add definition for IPC types, sending and receiving IPC messages
from aDSP, handling interrupt, sending different types of messages etc

Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>