usb: dwc2: fix a devres leak in hw_enable upon suspend resume

In the Linux kernel, the following vulnerability has been resolved:

usb: dwc2: fix a devres leak in hw_enable upon suspend resume

Each time the platform goes to low power, PM suspend / resume routines
call: __dwc2_lowlevel_hw_enable -> devm_add_action_or_reset().
This adds a new devres each time.
This may also happen at runtime, as dwc2_lowlevel_hw_enable() can be
called from udc_start().

This can be seen with tracing:
- echo 1 > /sys/kernel/debug/tracing/events/dev/devres_log/enable
- go to low power
- cat /sys/kernel/debug/tracing/trace

A new "ADD" entry is found upon each low power cycle:
... devres_log: 49000000.usb-otg ADD 82a13bba devm_action_release (8 bytes)
... devres_log: 49000000.usb-otg ADD 49889daf devm_action_release (8 bytes)
...

A second issue is addressed here:
- regulator_bulk_enable() is called upon each PM cycle (suspend/resume).
- regulator_bulk_disable() never gets called.

So the reference count for these regulators constantly increase, by one
upon each low power cycle, due to missing regulator_bulk_disable() call
in __dwc2_lowlevel_hw_disable().

The original fix that introduced the devm_add_action_or_reset() call,
fixed an issue during probe, that happens due to other errors in
dwc2_driver_probe() -> dwc2_core_reset(). Then the probe fails without
disabling regulators, when dr_mode == USB_DR_MODE_PERIPHERAL.

Rather fix the error path: disable all the low level hardware in the
error path, by using the "hsotg->ll_hw_enabled" flag. Checking dr_mode
has been introduced to avoid a dual call to dwc2_lowlevel_hw_disable().
"ll_hw_enabled" should achieve the same (and is used currently in the
remove() routine).