Code review comment for ~ethan.hsieh/+git/u-boot:devel

If I understand this correctly: since our u-boot isn't up-to-date, we're missing the 2 commits that migrate CONFIG_SYS_REDUNDAND_ENVIRONMENT (and others) to Kconfig, so those config changes were ignored on the defconfig.

This seems like a decent workaround for this, certainly feels safer than cherry-picking two rather big commits. Looks good to me.