UPSTREAM: usb: dwc3: core: simplify suspend/resume operations

UPSTREAM: usb: dwc3: core: simplify suspend/resume operations

now that we have re-factored dwc3_core_init() and
dwc3_core_exit() we can use them for suspend/resume
operations.

This will help us avoid some common mistakes when
patching code when we have duplicated pieces of code
doing the same thing.

Change-Id: I295c3b354123ce0449e7e4ee10e96fa444994488
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>
(cherry picked from commit 51f5d49ad6f011ee380b866ea617fd90584189a2)