Convert the driver to use the new SCU IPC API. This allows us to get rid
of the duplicate PMC IPC implementation which is now covered in SCU IPC
driver.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>