usb: dwc3: handshake between dwc3 and usb_bam for lpm

Adds the suspend/resume handshaking mechanism
(from previous devices) between the USB controller
and the USB BAM. This prevents
 - the controller from disabling clocks on the suspend flow
 - the USB BAM from accessing clocked off hardware in the resume flow

Change-Id: I5e8a93add03b27deaf60d2d17f43dd029dd9198f
Signed-off-by: Dov Levenglick <dovl@codeaurora.org>