usb: dwc2: Implement recovery after PM domain off

usb: dwc2: Implement recovery after PM domain off

According to the dt-bindings there are some platforms, which have a
dedicated USB power domain for DWC2 IP core supply. If the power domain
is switched off during system suspend then all USB register will lose
their settings.

Use GUSBCFG_TOUTCAL as a canary to detect that the power domain has
been powered off during suspend. Since the GOTGCTL_CURMODE_HOST doesn't
match on all platform with the current mode, additionally backup
GINTSTS. This works reliable to decide which registers should be
restored.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20250217134132.36786-4-wahrenst@gmx.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>