Simplify initialization logic by removing the usb_enabled()
check. The USB controller is part of the SoC, so it doesn't make
sense to create a system where it is not present.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Andrzej Zaborowski <balrogg@gmail.com>
Cc: qemu-arm@nongnu.org,
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1465419025-21519-2-git-send-email-ehabkost@redhat.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>