objtool: Avoid iterating !text section symbols

validate_functions() iterates all sections their symbols; this is
pointless to do for !text sections as they won't have instructions
anyway.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115119.346582716@infradead.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>