Set CONFIG_NOP_USB_XCEIV=m, needed for USB on Beagleboard-xm

Since 6022671 "ARM: OMAP3: Beagle: Adapt to ehci-omap changes" in
3.10-rc1, USB on BeagleBoard xM has required CONFIG_NOP_USB_XCEIV.
7c4ebe6 "USB: ehci-omap: Don't select any PHY driver" requires that the
option is selected in the config.

CONFIG_NOP_USB_XCEIV=y does not work, but I haven't been able to find
out why.

Enable CONFIG_NOP_USB_XCEIV as module to restore USB host and
networking,

Tested on BeagleBoard xM rev B.

Signed-off-by: Torstein Hegge <hegge@resisty.net>