We haven't used the functionality to pin BOs in a certain range at all
while the driver existed. Just nuke it.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>