drm/amdgpu: Add supported NPS modes node

Add sysfs node to show supported NPS mode for the
partition configuration selected using xcp_config

v2: Hide node if dynamic nps switch not supported

v3: Fix removal of files in case of error

Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>