Revert "usb: musb: dsps: remove explicit NOP device creation"

This reverts commit d8c3ef25.

Above mentioned change was made along with multi usb phy change and
adding DT support for nop transceiver. But other two changes did not
make it to mainline. This in effect makes dsps musb wrapper unusable
even for single instance.

Hence revert it so that at least single instance can be supported.

Cc: stable@vger.kernel.org # v3.7
Signed-off-by: Afzal Mohammed <afzal@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>