drm/amdgpu/gmc9: no need use kiq in vega10 tlb flush

two reasons:
1. there is a spinlock around;
2. vm register is pf/vf copy, vf can access via mmio safely.

Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>