This also re-enables the auto flashing for u-boot on the L5, but keeps
it disabled on the devkit for now until this u-boot supports the devkit
again.
[ci:skip-build] already built successfully in CI
This u-boot version doesn't support the devkit yet. Last I heard, Purism
plans to add the config back in after porting it from the old u-boot.
If anyone needs this (probably no one besides me?), the old u-boot can
be built locally from an earlier version of this package.