clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode

A 100MHZ 32-bit timer will be wrapped up less than 43s. Although the
kernel maintains a software high 32-bit count in the tick IRQ. But it's
not applicable to the user mode APPs.

Note: The kernel still uses the lower 32 bits of the timer.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200918132237.3552-9-thunder.leizhen@huawei.com