drm/amdgpu: remove extra parameter from amdgpu_ttm_bind() v2

We always use the BO mem now.

v2: minor rebase

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>