Revert "drm/amdkfd: only allow heavy-weight TLB flush on some ASICs for SVM too"

This reverts commit 36bf9321.

It causes SVM regressions on Vega10 with XNACK-ON. Just revert it
at the moment.

./kfdtest --gtest_filter=KFDSVMRangeTest.MigratePolicyTest

Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Philip <Yang&lt;Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>