SystemPacketBuffer reference counter possible overflow

[andyp-apple]

SystemPacketBuffer refcounts should be checked for overflow before incrementing:

connectedhomeip/src/system/SystemPacketBuffer.cpp

Lines 429 to 438 in 4f0ade5

	void PacketBuffer::AddRef()
	{
	#if CHIP_SYSTEM_CONFIG_USE_LWIP
	pbuf_ref(this);
	#else // !CHIP_SYSTEM_CONFIG_USE_LWIP
	LOCK_BUF_POOL();
	++this->ref;
	UNLOCK_BUF_POOL();
	#endif // !CHIP_SYSTEM_CONFIG_USE_LWIP
	}

[andyp-apple]

fix merged