usb: gadget: Fix Missing Function Wakeup notification sending on BAM wakeup

In Super-Speed mode, when the USB core wishes to issue remote wakeup due to
new data arriving on the BAM to BAM path, it needs to send Function Wakeup
notification to the USB host after the USB bus is resumed. However, the
sending of this notification fails when the USB core needs to wake up from
low-power mode, because the low-power mode exit is done asynchronously and
the sending of the Function Wakeup notification can not be done until the
USB bus is resumed.
This patch fixes this issue by checking whether the USB bus is suspended,
and if so, the sending Function Wakeup notification is delayed until the
USB bus is resumed.

Change-Id: I293476aaaf920b67fdbdf72a63524edc7a35750b
Signed-off-by: Danny Segal <dsegal@codeaurora.org>