arm64: perf: Only advertise cap_user_time for arch_timer

When sched_clock is running on anything other than arch_timer, don't
advertise cap_user_time*.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20200716051130.4359-5-leo.yan@linaro.org
Requested-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>