drm/amdgpu: enable Vega20 page queue support

Page queue is supported on Vega20 with SDMA firmware
123 onwards.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>