drm/nouveau/fault: Add support for GP10B

There is no BAR2 on GP10B and there is no need to map through BAR2
because all memory is shared between the GPU and the CPU. Add a custom
implementation of the fault sub-device that uses nvkm_memory_addr()
instead of nvkm_memory_bar2() to return the address of a pinned fault
buffer.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>