Cordio BLE: Dynamically calculate message length

The vendor specific HCI event can contain messages of arbitrary length,
thus the length of the message allocation must depend on the length of
the event.

connectivity/FEATURE_BLE/libraries/cordio_stack/ble-host/sources/hci/dual_chip/hci_evt.c

@@ -2738,6 +2738,7 @@ void hciEvtProcessMsg(uint8_t *pEvt)
   uint8_t   evt;
   uint8_t   subEvt;
   uint8_t   len;
+  uint8_t   extraMsgLen = 0;
   uint8_t   cbackEvt = 0;
   hciEvt_t  *pMsg;
   uint16_t  handle;
@@ -2997,6 +2998,7 @@ void hciEvtProcessMsg(uint8_t *pEvt)
 #endif
       hciEvtStats.numVendorSpecEvt++;
       cbackEvt = HCI_VENDOR_SPEC_CBACK_EVT;
+      extraMsgLen = len;
 
 #ifdef WSF_DETOKEN_TRACE
       if (WsfDetokenProcessHciEvent(len, pEvt))
@@ -3014,7 +3016,7 @@ void hciEvtProcessMsg(uint8_t *pEvt)
   if (cbackEvt != 0)
   {
     /* allocate temp buffer */
-    if ((pMsg = WsfBufAlloc(hciEvtCbackLen[cbackEvt])) != NULL)
+    if ((pMsg = WsfBufAlloc(hciEvtCbackLen[cbackEvt] + extraMsgLen)) != NULL)
     {
       /* initialize message header */
       pMsg->hdr.param = 0;