Remove ChromeOS specific configs from the U-Boot repository.

Remove ChromeOS specific configs from the U-Boot repository.

These configs now live in a separate repository
(u-boot-config.git) to reduce the patch load that we are
maintaining.  The config repository was created from the
u-boot-next repository using:

git filter-branch --subdirectory-filter include/configs/chromeos

This creates a repository of just the changes in that directory,
preserving the commit history.  The include/configs/tegra*.h config
files remain and are what are upstream.

Change-Id: I07176233be778bd6eb05733031643672b7b2ddd8

BUG=None
TEST=run "MAKEALL chromeos" without error. 

Additionally, I ran the following for Seaboad and Kaen

emerge-tegra2_<board> -auDN --selective=n chromeos-u-boot-next
cros_write_firmware --board tegra2_<board> --firmware /build/tegra2_<board>/u-boot/u-boot-recovery.bin --sign 
Verify system boots. 

This CL depends on: http://codereview.chromium.org/6756038/

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=8863bb3

[sjg, 2011-03-31 00:28:12]

LGTM

[Che-Liang Chiou, 2011-03-31 03:56:22]

LGTM.