ARM: imx25: set default phy_type and dr_mode for usbotg port

All currently supported i.MX25-based machines use phy_type = "utmi" and
dr_mode = "otg".  So this seems to be a sensible default.

This also doesn't hurt out-of-tree machines because up to now they had
to specify these two properties in the machine.dts which still takes
precedence by just overwriting the defaults added here.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>