ASoC: Intel: Add Intel SST audio DSP low level shim driver.

Add support for Intel Smart Sound Technology (SST) audio DSPs.
This driver provides the low level IO, reset, boot and IRQ management
for Intel audio DSPs. These files make up  the low level part of the SST
audio driver stack and will be used by many Intel SST cores like
Haswell, Broadwell and Baytrail.

SST DSPs expose a memory mapped region (shim) for config and control.
The shim layout is mostly shared without much modification across cores
and this driver provides a uniform API to access the shim and to enable
basic shim functions. It also provides functionality to abstract some shim
functions for cores with different shim features.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>