drm/ttm: fix warning that we shouldn't mix && and ||

Trivial warning fix.

Signed-off-by: Christian König <christian.koenig@amd.com>
Fixes: 44819136 ("drm/ttm: fix bulk_move corruption when adding a entry")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230623070935.65102-1-christian.koenig@amd.com