BBA/HLE: Fix random PCAP file corruption

Concurrency between RecvHandlePacket and SendFromDirectFIFO

Source/Core/Common/PcapFile.cpp

@@ -49,6 +49,7 @@ void PCAP::AddHeader(u32 link_type)
   m_fp->WriteBytes(&hdr, sizeof(hdr));
 }
 
+// Not thread-safe, concurrency between multiple calls to IOFile::WriteBytes.
 void PCAP::AddPacket(const u8* bytes, size_t size)
 {
   std::chrono::system_clock::time_point now(std::chrono::system_clock::now());