[coreboot] v3 patch rm elfboot

[Myles Watson]

This patch removes elfboot and references to ELF from v3.  Since lar
parses ELF, there's no need to have v3 parse ELF.  The ELF files that
v3 could parse should always have been a subset of the ones that lar
could parse anyway.

Myles

Signed-off-by: Myles Watson