drm: init TTM dev_mapping in ttm_bo_device_init()

drm: init TTM dev_mapping in ttm_bo_device_init()

With dev->anon_inode we have a global address_space ready for operation
right from the beginning. Therefore, there is no need to do a delayed
setup with TTM. Instead, set dev_mapping during initialization in
ttm_bo_device_init() and remove any "if (dev_mapping)" conditions.

Cc: Dave Airlie <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: Thomas Hellstrom <[email protected]>
Signed-off-by: David Herrmann <[email protected]>