u-boot: Add veyron jerry chromebook configs

This adds U-Boot configuration for a few white-label chromebooks, known
as "chromebook_jerry" in the U-Boot upstream defconfigs. It uses the
shared tree for the "veyron" baseboard. The config is almost the same as
upstream defconfig, but with REMAKE_ELF and POSITION_INDEPENDENT
enabled.

Untested since I don't have any of the veyron jerry chromebooks.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>