Seems the atm.ko module is part of the kernel, so it doesn't really matter which distro .. take your pick, and use what you're comfortable with.
If it's going to be used in a production environment and is going to used for a long time without updating, I'd go for Debian or Ubuntu 12.04 LTS .. but that's just *my* preference .. if you're more comfortable with a Red Hat based distro, use one
I do know that there are:-
atm-tools = Base programs for ATM in Linux, the net-tools for ATM
br2684ctl = Utility for configuring RFC 2684 ATM/Ethernet bridging
libatm1 = shared library for ATM (Asynchronous Transfer Mode)
in Ubuntu (so will also be in Debian)
but I'd expect them to be in all distros.