usb: dwc3: Change dwc3 irq to oneshot threaded irq

There is a possibility of dwc3 irq being fired as soon as
it gets enabled by tasklet handler. As a result dwc3 hard irq
handler disables the irq and schedules tasklet. If tasklet is
still running, tasklet_schedule becomes no op and dwc3 irq
remains disabled permanently. Fix this issue by handling irq
in threaded context with IRQF_ONESHOT flag set. Also update
the shared irq flag in xhci platform driver for irq registration
in HCD driver.

CRs-Fixed: 1038421
Change-Id: I9291cb08c4597922131b8c2d420e834a00a72621
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>