Great news - looks like you don't need a full 15.04 install, just the 3.19 kernel (that comes with 15.04) will do the job.
The steps in part (4) came from me, and I'm not sure this the best or correct way to install the 3.19 kernel on an Ubuntu 14.04 system. Perhaps someone else can let us know whether it is, and if it's not, offer a better way to install it.
The risk is, if this is a development PPA, that a future upgrade might install an experimental version of the linux kernel. But if that happens, you can always boot to GRUB and select the 3.19 you had before.