the procedure appears to be correct, but you should make sure there are no perepheral driers enabled in kernel that are using this pin. Please first try gpio_test and gpio_sysfs_test sample apps. See if they work as is. Then try to toggle GPIOs used in those apps (user buttons and user LEDs) from user space in the manner you describe above. once you have it working you can go back to GPIO you are trying to control.
GPIO_17 pad is already being configured to be used as user led 2 in mx53_ccwmx53js_io_init(), so we don’t need kernel changes. To drive it, we can do it from user space:
echo 204 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio204/direction
echo 1 > /sys/class/gpio/gpio204/value
echo 0 > /sys/class/gpio/gpio204/value
you should observe LED toggle at this point.