drm/amdkfd: report pcie bandwidth to the kfd

Similar to xGMI reporting the min/max bandwidth between direct peers, PCIe
will report the min/max bandwidth to the KFD.

Signed-off-by: Jonathan Kim <jonathan.kim@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>