GFX10 CP firmware expects PCIe atomics support. Don't enumerate GFX10
devices on platforms (PCIe v2) that don't support PCIe atomics.

Currently, some of the applications like clinfo soft hangs on platforms
without PCIe atomics support.

Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>