ARM: dts: hummingboard: Remove mention of nonexistent node

There is no pinctrl_usbotg_2 node in current Hummingboard dts files.
Drop reference to that.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>