Instead of overriding the whole do_compile function, just to reconfigure
u-boot for Trustfence, create a do_configure pre-function that takes care
of that. This allows the removal of duplicated code.
Also, disable the generation of u-boot environment artifacts. We are
not using them and so many u-boot artifacts in the deploy directory
are confusing.
Finally, adjust the names of the TF u-boot artifacts in the do_deploy
append function.
Signed-off-by: Javier Viguera <javier.viguera@digi.com>