Implement the IPC between Intel audio firmware and kernel driver. The
IPC allows transmission of requests, handling of responses as well as
unsolicited (i.e. firmware-generated) notifications.

A subscription mechanism is added to enable different parts of the
driver to register for specific notifications.

The part of the DSP boot process that involves sending ROM message
requires an extra step - must be followed by unstall operation of
MAIN_CORE. All other types of messages do not require such specific
handling, so separate set of functions is provided for sending these.
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20220311153544.136854-5-cezary.rojewski@intel.comSigned-off-by: Mark Brown <broonie@kernel.org>