Improve diagnostic when failing to lock old cards' clocks.

The issue is that the APIs we currently use don't support older
hardware. Users can still lookup the desired frequency for their
HW and manually lock clocks with nvidia-smi.

Author: alliepiper

nvbench/device_info.cu

@@ -131,7 +131,10 @@ catch (nvml::call_failed &e)
   {
     NVBENCH_THROW(std::runtime_error,
                   "GPU clock rates can only be modified for Volta and later. "
-                  "Device: {} ({}) SM: {} < {}",
+                  "Device: {} ({}) SM: {} < {}. For older cards, look up the "
+                  "desired frequency for your card and lock clocks manually "
+                  "with `nvidia-smi -lgc <freq_MHz>,<freq_MHz>` (or -rgc to "
+                  "unlock).",
                   this->get_name(),
                   this->get_id(),
                   this->get_sm_version(),