ARM: dts: omap3-beagle-xm: Add USB Host support

Provide RESET GPIO and Power regulator for the USB PHY,
the USB Host port mode and the PHY device for the controller.
Also provide pin multiplexer information for USB host pins.

We also relocate omap3_pmx_core pin definations so that they
are close to omap3_pmx_wkup pin definations.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>