usb: dwc3: core: Suspend PHYs on runtime suspend in host mode

Some PHY drivers (e.g. for Qualcomm QUSB2 and QMP PHYs) support
runtime PM to reduce PHY power consumption during bus_suspend.
Add changes to let core auto-suspend PHYs on host bus-suspend
using GUSB2PHYCFG register if needed for a platform. Also perform
PHYs runtime suspend/resume and let platform glue drivers e.g.
dwc3-qcom handle remote wakeup during bus suspend by waking up
devices on receiving wakeup event from PHY.

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>