be2net: cleanup MCC async event processing code

The MCC async event processing code has 2 issues:
a) because of long struct names the code indentation is badly broken
b) description and definitions of how an MCC completion is interpreted as
   an async event are confusing (for e.g. the last word of an MCC event is
   named "code", while "code" is just a sub-field of the last word.)

This patch fixes the structure definitions, comments and re-factors code
as needed.

Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>