usb: dwc3: fix PM resume error for rockchip platforms

usb: dwc3: fix PM resume error for rockchip platforms

We enable PM runtime auto suspend on rockchip platforms (e.g. rk3399),
it allows DWC3 controller to enter runtime suspend if usb cable detached.
So we don't need to do anything in dwc3_suspend() and dwc3_resume()
which duplicated the same operations as dwc3_runtime_suspend() and
dwc3_runtime_resume().

And if DWC3 controller works on HOST mode, we can't do runtime resume
DWC3 gadget.

Change-Id: I63e734f51b05274251d8a88a664eee768568eb7b
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>