binman: Support reading the offset of an ELF-file symbol

Binman needs to be able to update the contents of an ELF file after it has
been build. To support this, add a function to locate the position of a
symbol's contents within the file.

Fix the comments on bss_data.c and Symbol while we are here.

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