clocksource: ingenic: Add explicit include for cpuhotplug.h

clocksource: ingenic: Add explicit include for cpuhotplug.h

Removing include of cpu.h from of_device.h (included by of_platform.h)
causes an error in ingenic-timer:

drivers/clocksource/ingenic-timer.c: In function ‘ingenic_tcu_init’:
drivers/clocksource/ingenic-timer.c:338:15: error: implicit declaration of function ‘cpuhp_setup_state’

The of_platform.h header is not necessary either, so it and of_address.h
can be dropped.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230329-dt-cpu-header-cleanups-v1-11-581e2605fe47@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>