Queue CWSR area maybe registered to GPU as svm memory, create queue to
ensure svm mapped to GPU with KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED flag.

Add queue_refcount to struct svm_range, to track queue CWSR area usage.

Because unmap mmu notifier callback return value is ignored, if
application unmap the CWSR area while queue is active, pr_warn message
in dmesg log. To be safe, evict user queue.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>