logging: Use vsnprintk instead of vsnprintf
logging: Use vsnprintk instead of vsnprintf

The printk family of functions is used elsewhere, so make this
consistent. Also, printk has a smaller stack footprint.

Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

galak/zephyr,punitvara/zephyr,Vudentz/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,kraj/zephyr,kraj/zephyr,finikorg/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,kraj/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,punitvara/zephyr,finikorg/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,kraj/zephyr,nashif/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,GiulianoFranchetto/zephyr