Consistently use the reservation object wrappers instead of accessing
the ww_mutex directly.
Additional to that use the reservation object wrappers directly instead of
calling __ttm_bo_reserve with fixed parameters.
v2: fix typo
Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>