drm/amdgpu: allow multipipe policy on ASICs with one MEC

Always enable multipipe policy on ASICs with GC VERSION > 9.0.0
instead of MEC number > 1.

This will allow multipipe policy on ASICs with one MEC,
e.g., gfx11 APUs.

Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Aaron Liu <aaron.liu@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 6.1.x