mfd: fusb302: avoid sending notifier to USB/DP during PM suspend

mfd: fusb302: avoid sending notifier to USB/DP during PM suspend

When system enter PM suspend, it will use a flag genpd->suspend_
power_off to disable device power domain operations, and device
can't enable its power domain until complete PM resume, or rather,
until call pm_genpd_complete() to clear suspend_power_off flag.

In some case, e.g. plug in Type-C PD adapter during system suspend,
and then wakeup system, the fusb302 may send notifier to USB/DP
before USB/DP complete PM resume, this may cause USB/DP fail to
enable their power domain.

I don't find a way to make sure USB/DP PM resume, fortunately，
the PM framework provides a flag pm_freezing to indicate that
complete PM resume all of devices.

Change-Id: I5c9a467691956250c1fa99b7a83f5fe306c0730a
Signed-off-by: William Wu <wulf@rock-chips.com>