setup_board: migrate to new crossdev style
setup_board: migrate to new crossdev style

This allows us to simplify the code a bit.  Once this shakes out,
there is probably more improvements to be made.

BUG=chromium-os:26998
TEST=`cbuildbot chromiumos-sdk` works

Change-Id: I3f2775111da800622591c9b56ba00428d6106207
CQ-DEPEND=I25153be568e57596dd8ec90cd833da057e08a49a
Reviewed-on: https://gerrit.chromium.org/gerrit/16981
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

glevand/coreos--scripts,sigma/coreos-scripts,mjg59/scripts,smilart/scripts,BugRoger/scripts,fivethreeo/scripts,bcwaldon/coreos-scripts,gtank/scripts,zhang0137/scripts,smilart/scripts,fivethreeo/scripts,bcwaldon/coreos-scripts,andrejro/coreos--scripts,endocode/scripts,nicescale/scripts,endocode/scripts,smilart/scripts,vmware/coreos-scripts,bcwaldon/coreos-scripts,vmware/coreos-scripts,glevand/coreos--scripts,BugRoger/scripts,marineam/coreos-scripts,coreos/scripts,coreos/scripts,nicescale/scripts,gtank/scripts,nicescale/scripts,BugRoger/scripts,mischief/scripts,sigma/coreos-scripts,fivethreeo/scripts,mischief/scripts,mjg59/scripts,zhang0137/scripts,crawford/scripts,mjg59/scripts,mischief/scripts,vmware/coreos-scripts,crawford/scripts,crawford/scripts,andrejro/coreos--scripts,trnubo/scripts,trnubo/scripts,andrejro/coreos--scripts,zhang0137/scripts,marineam/coreos-scripts,sigma/coreos-scripts,marineam/coreos-scripts,endocode/scripts,gtank/scripts,trnubo/scripts