drm/amd/amdxcp: Use unique name for partition dev

drm/amd/amdxcp: Use unique name for partition dev

amdxcp is a platform driver for creating partition devices. libdrm
library identifies a platform device based on 'OF_FULLNAME' or
'MODALIAS'. If two or more devices have the same platform name, drm
library only picks the first device. Platform driver core uses name of
the device to populate 'MODALIAS'. When 'amdgpu_xcp' is used as the base
name, only first partition device gets identified. Assign unique name so
that drm library identifies partition devices separately.

amdxcp doesn't support probe of partitions, it doesn't bother about
modaliases.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>