binman: Enhance the map and fdt-update output

binman: Enhance the map and fdt-update output

At present the .map file produced for each image does not include the
overall image size. This is useful information.

Update the code to generate it in the .map file as well as the updated
FDT. Also fix a few comments while we are here.

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