UPSTREAM: usb: dwc3: core: re-factor init and exit paths

UPSTREAM: usb: dwc3: core: re-factor init and exit paths

The idea of this patch is for dwc3_core_init() to
abstract all the details about how to initialize
dwc3 and dwc3_core_exit() to do the same for
teardown.

With this, we can simplify suspend/resume operations
by a large margin and always know that we're going
to start dwc3 from a known starting point.

Change-Id: I3193f375fa153e1636de8f86fb752ef88afa5d95
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
(cherry picked from commit c499ff71ff2a281366c6ec7a904c547d806cbcd1)

Conflicts:
	drivers/usb/dwc3/core.c