drm/amdkfd: initialise kfd inside amdgpu_device_init

Also finalize kfd inside amdgpu_device_fini. kfd device_init needs
SRIOV exclusive accessing. Try to gather exclusive accessing to
reduce time consuming.

Signed-off-by: pding <Pixel.Ding@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>