drm/amdgpu: reset VM when an error is detected

When some problem with the updates of page tables is detected reset the
state machine of the VM and re-create all page tables from scratch.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>