USB: Fix double-linking of drivers/usb/otg when ULPI is selected

This patch corrects a problem where drivers/usb/otg is linked twice
if CONFIG_USB_ULPI is selected, resulting in a build error (symbol
conflict). The files in that directory are properly linked already
as part of CONFIG_USB, and need not be indicated specifically for
CONFIG_USB_ULPI.

Signed-off-by: Bill Gatliff <bgat@billgatliff.com>
Acked-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>