Add kconfig menus for most chipset VIDEO_MB values.

Add kconfig menus for most chipset VIDEO_MB values.

VIDEO_MB is a variable that defines how many MB of RAM will be used
for onboard graphics frame buffer. It's northbridge-dependent which
values for CONFIG_MB are valid (but not board-dependent).

This patch adds choices for menuconfig to select the VIDEO_MB value for:

 - Intel 82810
 - Intel 82830
 - VIA CN400
 - VIA CN700

Note: CN400 and CN700 are based on the CX700 datasheet, not sure if they're
correct. If somebody has CN400 and CN700 datasheets, please verify.

We drop all per-board VIDEO_MB variables in per-board Kconfig files as
there's a northbridge-specific option/default now (plus the user can override
the value if needed in menuconfig).

As CONFIG_MB is chipset-specific but not board-specific (and never was), filter
it in util/compareboard/compareboard, we don't need to match those values.

Finally, put "CPU", "Northbridge", "Southbridge", "Super I/O", and
"Devices" sections into the "Chipset" menu, where NB-specific
options will appear if you select a board using a certain NB,
SB-specific options would appear in the "Southbridge" section etc.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Myles Watson <mylesgw@gmail.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@4866 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1