drm/amdgpu: Remove IMU ucode in vf2pf

The IMU firmware is loaded on the host side, not the guest.
Remove IMU in vf2pf ucode id enum.

Signed-off-by: YuanShang <YuanShang.Mao@amd.com>
Reviewed-By: Horace Chen <horace.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>