drm/amdgpu: optimize amdgpu device attribute code

drm/amdgpu: optimize amdgpu device attribute code

unified amdgpu device attribute node functions:
1. add some helper functions to create amdgpu device attribute node.
2. create device node according to device attr flags on different VF mode.
3. rename some functions name to adapt a new interface.

v2:
1. remove ATTR_STATE_DEAD, ATTR_STATE_ALIVE enum.
2. rename callback function perform to attr_update.
3. modify some variable names

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>