Minimal support for viafb suspend/resume

This patch adds minimal support for suspend/resume of the
VIA framebuffer device. It requires a version of OFW
that restores the video mode.

This patch is OLPC-specific as the proper upstream solution
is to move the VIA video path to using the kernel modesetting
infrastructure and doing a proper save/restore in the kernel.

[jc: extensive changes for 2.6.34 merge]
Signed-off-by: Deepak Saxena <dsaxena@laptop.org>
[fts: viafb_driver moved from viafbdev.c to via-core.c]
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Cc: Joseph Chan <JosephChan@via.com.tw>