clocksource/drivers/ingenic: Fix section mismatch

The function ingenic_tcu_get_clock() is annotated for the __init
section but it is actually called from the online cpu callback.

That will lead to a crash if a CPU is hotplugged after boot time.

Remove the __init annotation for the ingenic_tcu_get_clock()
function.

Fixes: f19d838d

 (clocksource/drivers/ingenic: Add high resolution timer support for SMP/SMT)
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Link: https://lore.kernel.org/r/20201125102346.1816310-1-daniel.lezcano@linaro.org