tests: drivers: clock_control: api: nrf: Disable tests for nrf52832

On nrf52832 LF clock cannot be stopped during runtime because
it resets RTC COUNTER. Testsuite run on nrf clock control driver
assumes that it will not happen. Disabling testing of LF clock
for nrf52832.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>