[coreboot] duplicated code in Coreboot

[Bao, Zheng]

Since I started to work on the coreboot, I always sense that the much
code is duplicated. By duplicated, it doesn't mean the code in different
folders is almost same. As a matter of fact, it should be same. For
example, the most feature of it871(2,6,8) should be the same. But
it8712f_enable_serial doesn't use the first parameter dev, while
it8716f_enable_serial does. When the board changes the super io, you can
not just change the 2 to 6. You should also change the parameters. That
makes me confused.

This also happens on some chips which are close. Is it possible to fix
this in future?

Zheng