tests: benchmarks: mbedtls: Fix printf args
tests: benchmarks: mbedtls: Fix printf args

As printf() is now used directly instead of printf proxy function,
there's warning-as-error that long long is passed where %lu
expected, so cast it explicitly.

Signed-off-by: Paul Sokolovsky <35cb557f011771c94f127d6fef99f804b62203f5@linaro.org>

galak/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,nashif/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr