drm:amdgpu: enable IH ring1 for IH v7.0

We need IH ring1 for handling the pagefault
interrupts which over flow in default
ring for specific usecases.

Enable ring1 allows software to redirect
high interrupts to ring1 from default IH
ring.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>