objtool: Don't set 'jump_dest' for sibling calls

For most sibling calls, 'jump_dest' is NULL because objtool treats the
jump like a call and sets 'call_dest'.  But there are a few edge cases
where that's not true.  Make it consistent to avoid unexpected behavior.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/8737d6b9d1691831aed73375f444f0f42da3e2c9.1649718562.git.jpoimboe@redhat.com