MYNEWT-638: Bug when resetting controller while creating connection

This fix should address the issue where the controller was reset
while attempting to create a connection. It should now be possible
to create a connection after the reset. The bug was that a
global variable was not getting cleared which prevented
acceptance of the conn create command.

X-Original-Commit: c5c9b6e2e3f8aea74efd5ff99f7ed4334166e1c7

nimble/controller/src/ble_ll_conn.c

@@ -3176,6 +3176,9 @@ ble_ll_conn_module_reset(void)
         g_ble_ll_conn_comp_ev = NULL;
     }
 
+    /* Reset connection we are attempting to create */
+    g_ble_ll_conn_create_sm = NULL;
+
     /* Now go through and end all the connections */
     while (1) {
         connsm = SLIST_FIRST(&g_ble_ll_conn_active_list);