[VOL-3085]Add a new method to update default sampling frequency

Change-Id: I0261175ec441ecc93123f8ef05b27f3a4ab349cc
diff --git a/pkg/pmmetrics/performance_metrics.go b/pkg/pmmetrics/performance_metrics.go
index b5d9369..322126b 100644
--- a/pkg/pmmetrics/performance_metrics.go
+++ b/pkg/pmmetrics/performance_metrics.go
@@ -58,6 +58,11 @@
 	}
 }
 
+// UpdateFrequency will update the frequency.
+func (pm *PmMetrics) UpdateFrequency(frequency uint32) {
+	pm.frequency = frequency
+}
+
 // Metrics will store the PMMetric params
 func Metrics(pmNames []string) PmMetricsOption {
 	return func(args *PmMetrics) {