usb: dwc3: Fix recovery from power collapse

* Recovery from controller power collapse did not work properly
  as enumeration failed.
* Add power collapse flag to device tree specifying when cable is
  disconnected, whether or not power collapse should be performed.
* Add device tree flag to specify whether or not POR sequence
  after power collapse should be performed.

Change-Id: I16bf6f6b38adb1d6d6f5155732a7778a1318b822
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>