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 <[email protected]>
Reviewed-by: Hawking Zhang <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Kevin Wang