drm/ttm: Create pinned list

drm/ttm: Create pinned list

This list will be used to capture all non VRAM BOs not
on LRU so when device is hot unplugged we can iterate
the list and unmap DMA mappings before device is removed.

v2: Reanme function to ttm_bo_move_to_pinned
v3: Move the pinned list to ttm device

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>