Bumping open olt and core chart for 2.4 release

Change-Id: Id1282224c59008897f0b90cad70aba18a4bdba38
diff --git a/releases/voltha-2.4 b/releases/voltha-2.4
index c37fc80..71b0252 100644
--- a/releases/voltha-2.4
+++ b/releases/voltha-2.4
@@ -3,9 +3,9 @@
 #
 # Source this file before running ./voltha up to install the VOLTHA 2.4.0 release
 
-export VOLTHA_CHART_VERSION=2.5.4
+export VOLTHA_CHART_VERSION=2.5.6
 export VOLTHA_BBSIM_CHART_VERSION=3.1.0
-export VOLTHA_ADAPTER_OPEN_OLT_CHART_VERSION=2.5.6
+export VOLTHA_ADAPTER_OPEN_OLT_CHART_VERSION=2.5.8
 export VOLTHA_ADAPTER_OPEN_ONU_CHART_VERSION=2.4.5
 export ONOS_CLASSIC_CHART_VERSION=0.1.1
 export RADIUS_CHART_VERSION=1.0.1