ARM: dts: imx23-olinuxino: Fix polarity of LED GPIO

On imx23-olinuxino the LED turns on when level logic high is aplied to
GPIO2_1.

Fix the gpios property accordingly.

Fixes: b34aa185 ("ARM: dts: imx23-olinuxino: Remove unneeded "default-on"")
Reported-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: stable@vger.kernel.org
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>