objtool: Fix weak symbol hole detection for .cold functions

objtool: Fix weak symbol hole detection for .cold functions

When ignore_unreachable_insn() looks for weak function holes which jump
to their .cold functions, it assumes the parent function comes before
the corresponding .cold function in the symbol table.  That's not
necessarily the case with -ffunction-sections.

Mark all the holes beforehand (including .cold functions) so the
ordering of the discovery doesn't matter.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>