`packet_rx_drop_count` in pymavlink/generator/C/include_v1.0/mavlink_types.h is always 0

The only usage is in the `generator/C/include_v1.0/mavlink_helpers.h` is at line 378 and it is an initialization. The code actually counting the number of dropped packed is commented out (and not working). I can try to fix it and make PR but I am using this library for the first day, so I will need someone to check it after me. Should I give it a try?

Start in pymavlink/generator/C/include_v1.0/mavlink_types.h and inspect the initialization in generator/C/include_v1.0/mavlink_helpers.h at line 378, along with the commented-out packet-drop counting code. Determine how the counter should be updated and verify that the reported drop count is no longer always zero.

Written by the indexing model from the issue text.