binman: Don't depend on dict order in ELF testOutsideFile()

binman: Don't depend on dict order in ELF testOutsideFile()

At present this test assumes that the symbols are returned in address
order. However, objdump can list symbols in any order and dictionaries do
not guarantee any particular order when iterating through item.

Update elf.GetSymbols() to return an OrderedDict, sorted by address, to
avoid any problems.

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