Bluetooth: Make HciPacketizer reusable

Test: VtsHalBluetoothV1_0TargetTest passes
Change-Id: I480d156225af2a5dd879f47a897af0b01dab5663
diff --git a/bluetooth/1.0/default/hci_internals.h b/bluetooth/1.0/default/hci_internals.h
index d5714be..1e1f300 100644
--- a/bluetooth/1.0/default/hci_internals.h
+++ b/bluetooth/1.0/default/hci_internals.h
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <stdlib.h>
+
 // HCI UART transport packet types (Volume 4, Part A, 2)
 enum HciPacketType {
   HCI_PACKET_TYPE_UNKNOWN = 0,