logging: Add LOG_RAW macro

Add macro for logging raw formatted string. It is similar to
LOG_PRINTK macro but contrary to LOG_PRINTK it should not append
carriage return character to any new line character found in the
string. LOG_PRINTK processed by log_output module has that to
mimic printk behavior.

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