drm/amdgpu: enable IH ring 1 and ring 2 for navi

Support added into IH to enable ring1 and ring2 for navi10_ih.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>