Add venus-3.0 to venus directory list

Add a directory for Venus version 3.0, as found on some MSM8909 devices. When support for Venus on MSM8909 lands in the mainline kernel (or in the MSM8909 mainline fork), this will be needed for MSM8909 devices that store the Venus firmware in the root of the modem partition. I'm not sure if such devices exist, but I think this directory should be added anyway to be consistent.