Revert "drm/amdkfd: Make TLB flush conditional on mapping"

This reverts commit 31f33243.

Reason for revert: it causes regressions on several Asics.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>