twister: rename variable p to log_root
twister: rename variable p to log_root

The variable p represents the name of a platform, it shouldn't be
reassigned

Signed-off-by: Jingru Wang <4cb10c79090f98ea35a3501436f2c4a683df303f@synopsys.com>

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