boards: arc: Load Elf with OpenOCD by default

Now when ARC development boards are switched to generic OpenOCD
runner we need to explicitly instruct the runner to load Elf but not
binary image (which is a default for OpenOCD runner).

This might be done either manually adding "--use-elf" option to
west's command line or that might be added by default fro affected
boards, which we do exactly now.

Fixes https://github.com/zephyrproject-rtos/zephyr/issues/22888

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Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>