Update segger with a change in SEGGER_RTT_Conf.h that allows to use DT memory section for RTT data. Added help section to SEGGER_RTT_SECTION_CUSTOM_DTS_REGION Kconfig explaining what alias need to be added to DTS. Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>