drm/ttm: use phys_addr_t for ttm_bus_placement

Fixes ttm on platforms like PPC460 where the CPU
is in 32-bit mode, but the physical addresses are
>32 bits.

Extracted from a patch by Hans Verkuil.
Tested-by: NJulian Margetson <runaway@candw.ms>
Acked-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Julian Margetson <runaway@candw.ms>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

include/drm/ttm/ttm_bo_api.h

@@ -92,7 +92,7 @@ struct ttm_placement {
  */
 struct ttm_bus_placement {
 	void		*addr;
-	unsigned long	base;
+	phys_addr_t	base;
 	unsigned long	size;
 	unsigned long	offset;
 	bool		is_iomem;