bcmxcp: Output more info hardware capabilities in debug mode

Add some more debug output on driver init, to let us know what the hardware support.
Outputs length of alarm history log, topology block length and maximum supported command length.
bcmxcp: Initialize variables in calculate_ups_load method
bcpmxp: Add support for reading topology map and setting ups.description based on it
Merge branch 'bcmxcp' of https://github.com/alfh/nut into bcmxcp