binman: Show the image name for the top-level section

At present we show 'main section' as the top-level section name. It may
be more helpful to show the actual image name. This is tricky because
Image is a parent class of Entry_section, so there is no distinction
between an image and a section.

Update it to show the image name.

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

tools/binman/image.py

@@ -77,7 +77,7 @@ class Image(section.Entry_section):
                  generate=True):
         super().__init__(None, 'section', node, test=test)
         self.copy_to_orig = copy_to_orig
-        self.name = 'main-section'
+        self.name = name
         self.image_name = name
         self._filename = '%s.bin' % self.image_name
         self.fdtmap_dtb = None