rpk tuning: allow clocksource to fail

clocksource isn't available on Azure nor on ARM.

As follow up, we should figure out which clocksource to actually use,
but for now we can just allow failure.

Closes #6290

src/go/rpk/pkg/cli/cmd/redpanda/tune/tune.go

@@ -194,7 +194,8 @@ func tune(
 			results = append(results, result{tunerName, false, enabled, supported, reason})
 			// We exit with code 1 when it's enabled and not supported except
 			// for disk_write_cache since it's only supported for GCP.
-			exit1 = exit1 || enabled && !supported && tunerName != "disk_write_cache"
+			// We also allow clocksource to fail, see #6444.
+			exit1 = exit1 || enabled && !supported && !(tunerName == "disk_write_cache" || tunerName == "clocksource")
 			continue
 		}
 		log.Debugf("Tuner parameters %+v", params)