gpu: nvgpu: improve nvs uapi

- Make the domain scheduler timeslice type nanoseconds to future proof
  the interface
- Return -ENOSYS from ioctls if the nvs code is not initialized
- Return the number of domains also when user supplied array is present
- Use domain id instead of name for TSG binding
- Improve documentation in the uapi headers
- Verify that reserved fields are zeroed
- Extend some internal logging
- Release the sched mutex on alloc error
- Add file mode checks in the nvs ioctls. The create and remove ioctls
  require writable file permissions, while the query does not; this
  allows filesystem based access control on domain management on the
  single dev node.

Jira NVGPU-6788

Change-Id: I668eb5972a0ed1073e84a4ae30e3069bf0b59e16
Signed-off-by: Konsta Hölttä <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2639017
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-cert <svc-mobile-cert@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit

drivers/gpu/nvgpu/os/linux/ioctl_tsg.c

@@ -181,7 +181,23 @@ static int nvgpu_tsg_bind_scheduling_domain(struct nvgpu_tsg *tsg,
 		struct nvgpu_tsg_bind_scheduling_domain_args *args)
 {
 
-	return nvgpu_tsg_bind_domain(tsg, args->domain_name);
+	if (args->reserved[0] != 0) {
+		return -EINVAL;
+	}
+
+	if (args->reserved[1] != 0) {
+		return -EINVAL;
+	}
+
+	if (args->reserved[2] != 0) {
+		return -EINVAL;
+	}
+
+	if (tsg->g->scheduler == NULL) {
+		return -ENOSYS;
+	}
+
+	return nvgpu_tsg_bind_domain(tsg, args->domain_id);
 }
 #endif