s_rtc_isr_noniram_hook() function

This helper function can be used to avoid the interrupt to be triggered with cache disabled. There are lots of different signals on RTC module (i.e. sleep_wakeup, wdt, brownout_detect, etc.) We might want some of them can be triggered with cache disabled, some are not. Therefore, this function is created to avoid those which do not want to be triggered with cache disabled.