Different api_version suggests different kernel driver used and
different interface is used to communication with the hardware.

Allow setting platform specific callbacks based on api_version.

Currently, all platforms with api_version 1 uses Mbox/MMIO interfaces.

No functional changes are expected.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
[srinivas.pandruvada@linux.intel.com: changelog edits]
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>