freedreno/drm/virtio: Use global_faults

Rather than doing a synchronous round trip to the host to query fault
count, use the shmem->global_faults field if available.  The kernel is
already only reporting faults associated with the same drm_file (which
in this case maps 1:1 to guest process), so the only thing we really
miss is, if the app is using multiple contexts, _which_ context the
fault was in.  But vulkan doesn't even use that, which sounds like a
good enough argument that per-submitqueue granularity isn't really
needed.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23533>