elf.rs: do not inline constant from goblin library
elf.rs: do not inline constant from goblin library

SELFMAG is declared [here](https://github.com/m4b/goblin/blob/de8aecc8f1e7f3de7d66a1511d3976cdf0335e0c/src/elf/header.rs#L91).
redox-os/kernel,AleVul/kernel,AleVul/kernel,redox-os/kernel,redox-os/kernel