binman: Centralise device-tree updates within binman

binman: Centralise device-tree updates within binman

At present we have a few calls to device-tree functions in binman and plan
to add more as we add new entry types which need to report their results.

It makes sense to put this code in a central place so that we can make
sure all device trees are updated. At present we only have U-Boot proper,
but plan to add SPL and TPL too.

Signed-off-by: Simon Glass <sjg@chromium.org>