usb: gadget: f_mass_storage: Add delay before continuing status stage

There is a possibility of race between ep0 setup phase completion
handler and mass storage thread. Upon set_alt if thread gets a
chance to run before dwc3_ep0_delegate_req() returns
USB_GADGET_DELAYED_STATUS and sets delayed_status flag to true status
phase request never gets queued. This results into device enumeration
failure followed by a bus resets. Fix this issue by adding delay before
calling usb_composite_setup_continue() to queue the status phase request.

Change-Id: Iec6cf668053af310be5171d19d204fb452e01f2a
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>