drm/amdgpu: select HDP ref/mask according to gfx ring pipe

Use correct ref/mask for differnent gfx ring pipe.
This should fix the gfx hang issue after enabling gfx pipe1.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2117


Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: ZhenGuo Yin <zhenguo.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>