clocksource/drivers/arch_arm_timer: Move workaround synchronisation around

mainline inclusion
from mainline-v5.16-rc1
commit db26f8f2
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4QCBG


CVE: NA

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

We currently handle synchronisation when workarounds are enabled
by having an ISB in the __arch_counter_get_cnt?ct_stable() helpers.

While this works, this prevents us from relaxing this synchronisation.

Instead, move it closer to the point where the synchronisation is
actually needed. Further patches will subsequently relax this.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211017124225.3018098-14-maz@kernel.org


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>