soc: nordic: common: mram_latency: Add option to auto request no latency

Add CONFIG_MRAM_LATENCY_AUTO_REQ. When option is enabled then module
requests no latency during the initialization. This option might be
useful for cases where we want to achieve maximum performance and
want to avoid controlling MRAM in the code.

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