drm/amdgpu: don't use kiq to flush gpu tlb if mes enabled

If MES is enabled, don't use kiq to flush gpu tlb,
for it would result in conflicting with mes fw.

Signed-off-by: Jack Xiao <Jack.Xiao@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>