local.conf: add machine selections, default device tree for colibri
local.conf: add machine selections, default device tree for colibri

Signed-off-by: Jason Liu <76a57ac72627ac6bc35b47c28a9937340c51b1c2@gumstix.com>

gumstix/meta-gumstix-extras,gumstix/meta-gumstix-extras,gumstix/meta-gumstix-extras