[coreboot] [RFC] Remove empty mainboard.c files up for review

[Paul Menzel]

Dear coreboot folks,

I pushed change set I379e4b1e1b1725648c6231bc6954ac3cc655a596
(mainboard: Remove empty mainboard.c files) [1] for review.

```
mainboard: Remove empty mainboard.c files

All the deleted mainboard files contain no code besides some print
statements denoting, that the init is executed.

If such statements are desired, this should be done in common code so it
does not have to be added to each mainboard.

Therefore, also delete files with just print statements.
```

Please voice any objections.

Thanks,

Paul

[1] http://review.coreboot.org/#/c/12355/