2
there is no configuration option for this.
I assume you still want people with particular ip's to log in with a password, but only people from those certain ip's can turn on the auto-login option.
Easiest way I can think of is to modify the autologin code (see the wiki for how to enable this code) and add some code to only show the auto-login check box for particular ip addresses.
I'd probably add code to the cookie saving part to ensure only particular ip's get the auto-save cookie create (prevents problem with people hacking in the auto-login info from outside the form).
If you're looking to have people from particular ip's automatically logged in without having a password I highly recommend against this. IP's are easily spoofed.