drm: bridge/dw-hdmi-ahb-audio: use strscpy() is more robust and safer

The implementation of strscpy() is more robust and safer.

That's now the recommended way to copy NUL terminated strings.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220919030401.211331-1-chi.minghao@zte.com.cn