Spidernet cleanup un-needed API

There is no need to pass a flag into spider_net_decode_one_descr()
so remove this, and perform some othre minor cleanup.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>