usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM_NONE

This is an attempt to rehash commit 0cf884e8 ("usb: dwc2: add bus
suspend/resume for dwc2") on ToT.  That commit was reverted in commit
b0bb9bb6 ("Revert "usb: dwc2: add bus suspend/resume for dwc2"")
because apparently it broke the Altera SOCFPGA.

With all the changes that have happened to dwc2 in the meantime, it's
possible that the Altera SOCFPGA will just magically work with this
change now.  ...and it would be good to get bus suspend/resume
implemented.

This change is a forward port of one that's been living in the Chrome
OS 3.14 kernel tree.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>