Fix HCI parser and packetizer

Issue found from the test H4ProtocolAsyncTest#TestMultiplePackets.
The packetizer does not correctly handle a packet termination
at the beginning of a chunk.

Test: atest --host bluetooth-vendor-interface-hci-test
Bug: 276652301
Change-Id: I1b61efcfa5f817fdb8b5870e81d660be5279fdea
diff --git a/bluetooth/hci/h4_protocol.cc b/bluetooth/hci/h4_protocol.cc
index 51a624f..5f6d86e 100644
--- a/bluetooth/hci/h4_protocol.cc
+++ b/bluetooth/hci/h4_protocol.cc
@@ -105,15 +105,12 @@
       buffer_offset += 1;
     } else {
       bool packet_ready = hci_packetizer_.OnDataReady(
-          hci_packet_type_, input_buffer, buffer_offset);
+          hci_packet_type_, input_buffer, &buffer_offset);
       if (packet_ready) {
-        // Call packet callback and move offset.
-        buffer_offset += OnPacketReady(hci_packetizer_.GetPacket());
+        // Call packet callback.
+        OnPacketReady(hci_packetizer_.GetPacket());
         // Get ready for the next type byte.
         hci_packet_type_ = PacketType::UNKNOWN;
-      } else {
-        // The data was consumed, but there wasn't a packet.
-        buffer_offset = input_buffer.size();
       }
     }
   }