drm/amdkfd: Only apply heavy-weight TLB flush on Aldebaran

It is to workaround HW bug on other Asics and based on
reverting two commits back:
  drm/amdkfd: Add heavy-weight TLB flush after unmapping
  drm/amdkfd: Add memory sync before TLB flush on unmap

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