biology/linux-foldingathome: Fix WRKSRC paths

After the recent changes to DISTNAME, the paths to files in WRKSRC were
no longer correct. Use DISTNAME:T to use the part of DISTNAME that we
actually need.

Reported by: pkg-fallout
Fixes: 6086ff0b3283 biology/linux-foldingathome: Add support for aarch64