drm/amdgpu: enable ASPM support for PCIE 7.4.0/7.6.0

Enable ASPM support for PCIE 7.4.0 and 7.6.0.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>