arm: omap4: usb: explicitly configure MUSB pads

Use the mux framework APIs to explicitly configure
the MUSB pads. The MUSB controller in OMAP4 can use
either the old ULPI interface, or the new internal PHY.
Configure the pads accordingly.

Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>