Just allocate the GART space and fill it.

This prevents forcing the BO to be idle.

v2: don't unbind/bind at all, just fill the allocated GART space
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>