nimble/host: Fix checking for NOP in ble_hs_hci_rx_evt

NOP can be sent as Command Complete or Command Status. Those events
don't have opcode field in same place so old code was not checking
proper bytes. It looks like this never worked for Command Status case.

nimble/host/src/ble_hs_hci.c

@@ -356,28 +356,29 @@ ble_hs_hci_rx_ack(uint8_t *ack_ev)
 int
 ble_hs_hci_rx_evt(uint8_t *hci_ev, void *arg)
 {
+    struct ble_hci_ev *ev = (void *) hci_ev;
+    struct ble_hci_ev_command_complete *cmd_complete = (void *) ev->data;
+    struct ble_hci_ev_command_status *cmd_status = (void *) ev->data;
     int enqueue;
 
     BLE_HS_DBG_ASSERT(hci_ev != NULL);
 
-    switch (hci_ev[0]) {
+    switch (ev->opcode) {
     case BLE_HCI_EVCODE_COMMAND_COMPLETE:
+        enqueue = (cmd_complete->opcode == BLE_HCI_OPCODE_NOP);
+        break;
     case BLE_HCI_EVCODE_COMMAND_STATUS:
-        if (hci_ev[3] == 0 && hci_ev[4] == 0) {
-            enqueue = 1;
-        } else {
-            ble_hs_hci_rx_ack(hci_ev);
-            enqueue = 0;
-        }
+        enqueue = (cmd_status->opcode == BLE_HCI_OPCODE_NOP);
         break;
-
     default:
         enqueue = 1;
         break;
     }
 
     if (enqueue) {
         ble_hs_enqueue_hci_event(hci_ev);
+    } else {
+        ble_hs_hci_rx_ack(hci_ev);
     }
 
     return 0;