move get_srv_psk_list

It can be reused in other test-suites

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/tests/opt-testcases/tls13-kex-modes.sh b/tests/opt-testcases/tls13-kex-modes.sh
index 4f62ed6..b1320c5 100755
--- a/tests/opt-testcases/tls13-kex-modes.sh
+++ b/tests/opt-testcases/tls13-kex-modes.sh
@@ -18,15 +18,6 @@
 # limitations under the License.
 #
 
-get_srv_psk_list ()
-{
-    case $(( TESTS % 3 )) in
-        0) echo "psk_list=abc,dead,def,beef,Client_identity,6162636465666768696a6b6c6d6e6f70";;
-        1) echo "psk_list=abc,dead,Client_identity,6162636465666768696a6b6c6d6e6f70,def,beef";;
-        2) echo "psk_list=Client_identity,6162636465666768696a6b6c6d6e6f70,abc,dead,def,beef";;
-    esac
-}
-
 requires_gnutls_tls1_3
 requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_3
 requires_config_enabled MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index a75b3f5..f264b5e 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1024,6 +1024,16 @@
     esac
 }
 
+# Generate random psk_list argument for ssl_server2
+get_srv_psk_list ()
+{
+    case $(( TESTS % 3 )) in
+        0) echo "psk_list=abc,dead,def,beef,Client_identity,6162636465666768696a6b6c6d6e6f70";;
+        1) echo "psk_list=abc,dead,Client_identity,6162636465666768696a6b6c6d6e6f70,def,beef";;
+        2) echo "psk_list=Client_identity,6162636465666768696a6b6c6d6e6f70,abc,dead,def,beef";;
+    esac
+}
+
 # Determine what calc_verify trace is to be expected, if any.
 #
 # calc_verify is only called for two things: to calculate the