clocksource/drivers/arm_arch_timer: Remove fsl-a008585 parameter

Having a command line option to flip the errata handling for a
particular erratum is a little bit unusual, and it's vastly superior to
pass this in the DT. By common consensus, it's best to kill off the
command line parameter.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
[Mark: split patch, reword commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>