runners: openocd: prefer extended-remote for gdb connection
runners: openocd: prefer extended-remote for gdb connection

Instead of deprecated 'target remote'.
Fix:
Warn : Prefer GDB command "target extended-remote :3333"
instead of "target remote :3333"

Signed-off-by: Julien Massot <ad45d338e0f9dc7767e692227f7b2fcd41b31818@iot.bzh>

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