Lets update our TODO

Hi.

It's terrible, please help updating it.
(It can be a real PITA, when someone new comes, and can't pick any real
work from TODO)

Changes:
register_reboot_notifier() always returns 0
skb_alloc doesn't exist
there is no get_free_pages() (replace it with __get_free_page[s]?()) init_etherdev() doesn't exist
ips, ip2main look bogus, ips_detect does not kmalloc anything;

There's a comment in isapnp/core.c that release_region's were added (dated 2001-06-03!).
proc_register() is now static, used by internal procfs routines.

loops_per_sec is no more.