Do not power on if no video

Power on the device on start only if video capture is enabled.

Note that it only impacts display mirroring, since control is completely
disabled if video source is camera.

Refs 110b3a16f6

app/src/cli.c

@@ -2398,6 +2398,8 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
 
     if (!opts->video) {
         opts->video_playback = false;
+        // Do not power on the device on start if video capture is disabled
+        opts->power_on = false;
     }
 
     if (!opts->audio) {