ARM: dts: imx23-olinuxino: Fix dr_mode of usb0

The dr_mode of usb0 on imx233-olinuxino is left to default "otg".
Since the green LED (GPIO2_1) on imx233-olinuxino is connected to the
same pin as USB_OTG_ID it's possible to disable USB host by LED toggling:

echo 0 > /sys/class/leds/green/brightness
[ 1068.890000] ci_hdrc ci_hdrc.0: remove, state 1
[ 1068.890000] usb usb1: USB disconnect, device number 1
[ 1068.920000] usb 1-1: USB disconnect, device number 2
[ 1068.920000] usb 1-1.1: USB disconnect, device number 3
[ 1069.070000] usb 1-1.2: USB disconnect, device number 4
[ 1069.450000] ci_hdrc ci_hdrc.0: USB bus 1 deregistered
[ 1074.460000] ci_hdrc ci_hdrc.0: timeout waiting for 00000800 in 11

This patch fixes the issue by setting dr_mode to "host" in the dts file.

Reported-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Peter Chen <peter.chen@freescale.com>
Fixes: b4931294 ("ARM: dts: imx23-olinuxino: Add USB host support")
Cc: stable@vger.kernel.org
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>