* Drop unnecessary device tree utilities
They have been used for Barebox which uses device tree to configure the
state storage and its location. With the change to GRUB the tools are no
longer required.
* Determine manual GRUB update depending on installed tools
Manually update the GRUB environment if no grub environment tools are
installed. This makes a upgrade work even after a previous downgrade (in
that case a grubenv file might still be present in the UEFI ESP).
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