base-files: tune fragment queue thresholds for available system memory

base-files: tune fragment queue thresholds for available system memory

The default fragment low/high thresholds are 3 and 4 MB. On devices with
only 32MB RAM, these settings may lead to OOM when many fragments that
cannot be reassembled are received. Decrease fragment low/high thresholds
to 384 and 512 kB on devices with less than 64 MB RAM.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>