x86, objtool: Dont exclude arch/x86/realmode/

Specifically, init.c uses jump_labels.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210506194157.516200011@infradead.org