[coreboot] initial Kconfig support for epia-n and via CPUs

[Myles Watson]

> I have a question about the mainboard stuff. We want mainboard Kconfig
> files in the mainboards, not in the next-level-up directory. But I
> don't know how to get choice to work in the expected way. Please see
> src/mainboard/via/Kconfig and
> src/via/mainboard/*/Kconfig to see what I mean.

-        help
-          Kontron 986LCD-M Series mainboards
 endchoice
 
-config MAINBOARD_DIR
-	string
-	default via/vt8454c
-	depends on BOARD_VIA_VT8454C
+source "src/mainboard/via/vt8454c/Kconfig"
+source "src/mainboard/via/epia-n/Kconfig"

I tried putting the end choice after the source statements and it looked
more like what I think you want.

+source "src/mainboard/via/vt8454c/Kconfig"
+source "src/mainboard/via/epia-n/Kconfig"
 endchoice

Thanks,
Myles