drm/amd: Add get_fw_version to kfd-->kgd interface

This patch adds a new interface to the kfd-->kgd interface.
The new interface function retrieves the firmware version that is currently in
use by the MEC engine. The firmware was uploaded to the MEC engine by the kgd
(radeon).

v2: Added parameter of engine type to interface function

Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>