drm/amdgpu: Fix always_valid bos multiple LRU insertions.

If these bos are evicted and are in the validated list
things blow up, so do not put them in there. Notably,
that tries to add the bo to the LRU twice, which results
in a BUG_ON in ttm_bo.c.

While for the bo_list an alternative would be to not allow
always valid bos in there, that does not work for the user
fence.

v2: Fixed whitespace issue pointed out by checkpatch.pl

Signed-off-by: Bas Nieuwenhuizen <basni@chromium.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org