IMU is a new firmware for GFX11.

There are four means by which firmware version can be queried
from the driver: device attributes, vf2pf, debugfs,
and the AMDGPU_INFO_FW_VERSION option in the amdgpu info ioctl.

Add IMU as an option for those four methods.

V2: Added debugfs
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>