usb: dwc3: omap: drop DEV_PM_OPS for now

We need to have actual HW in order to implement
and test that part of the code anyway. Until then
it's best to remove it.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>