arm64: Run ARCH_WORKAROUND_1 enabling code on all CPUs

stable inclusion
from linux-4.19.155
commit d953cd3fb149a999534ff48af323eb091fd5aa3b

--------------------------------

commit 18fce561 upstream.

Commit 73f38166 ("arm64: Advertise mitigation of Spectre-v2, or lack
thereof") changed the way we deal with ARCH_WORKAROUND_1, by moving most
of the enabling code to the .matches() callback.

This has the unfortunate effect that the workaround gets only enabled on
the first affected CPU, and no other.

In order to address this, forcefully call the .matches() callback from a
.cpu_enable() callback, which brings us back to the original behaviour.

Fixes: 73f38166 ("arm64: Advertise mitigation of Spectre-v2, or lack thereof")
Cc: <stable@vger.kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>