usb: gadget: mv_u3d: remove outdated selects

USB_GADGET_{DUAL,SUPER}SPEED symbols have
been removed by commit 85b8614d

 (usb: gadget:
get rid of USB_GADGET_{DUAL,SUPER}SPEED), for
some reason mv_u3d_core was lost.

Remove those selects now.

Signed-off-by: Felipe Balbi <balbi@ti.com>