i'm pretty sure that, since easy debian doesn't "install" debian on the device, but only chroots into a mounted image, it doesn't have it's own kernel, let alone modules. and even if it had, they wouldn't be used, same with the init system. it merely uses the underlying maemo (still linux); you can think of it as of (maemo kernel + debian userspace), even if it's not 100% correct. if you have ever used chroots you would be familiar with this stuff, but anyway just put that module into diablo and modprobe it, then chroot into debian.

EDIT: also, use modprobe unless you know what you're doing, since insmod DOESN'T handle modules dependencies, and you might run into funny stuff