usb: core: Resume the bus for FREEZE pm_event too

Currently the driver resumes the USB bus from runtime suspend
if PM_SUSPEND event is triggered, so that proper wakeup setting
can be done. Do the same for PM_FREEZE usecase as well so as to
allow power collapse of USB core to happen as a part of pm_freeze
on platforms which require hibernation (suspend to disk) feature.

Change-Id: I0a25cd42afb381eb7a984f6634ac620479e17978
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>