This patch adds a code that implements communication channel between the
driver and the firmware.

Acked-by: John Griffin <john.griffin@intel.com>
Reviewed-by: Bruce W. Allan <bruce.w.allan@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>