samples: posix: eventfd: bugfix for regex check
samples: posix: eventfd: bugfix for regex check

Bugfix for regex adding "\\" before "(" and ")" for proper regex parsing

Signed-off-by: Maciej Perkowski <cb34e965b6a5a3425eafdbd0feb7e469ae1417ea@nordicsemi.no>

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