gsm0808: make gsm0808_create_reset_ack() accessible

The create function to generate the RESET ACKNOWLEDGE
message is not accessible from outside, as it does not
appear in limosmogsm.map. It also has not testcase.

This commit adds gsm0808_create_reset_ack() to the
map file and also adds a testcase.

Change-Id: I82d3411484f82b4a9205d407fa0442244678f183
diff --git a/tests/gsm0808/gsm0808_test.ok b/tests/gsm0808/gsm0808_test.ok
index 52af134..e101d65 100644
--- a/tests/gsm0808/gsm0808_test.ok
+++ b/tests/gsm0808/gsm0808_test.ok
@@ -2,6 +2,7 @@
 Testing creating Layer3
 Testing creating Layer3 (AoIP)
 Testing creating Reset
+Testing creating Reset Ack
 Testing creating Clear Command
 Testing creating Clear Complete
 Testing creating Chipher Mode Command