usb: cdns3: Removes xhci_cdns3_suspend_quirk from host-export.h

Function xhci_cdns3_suspend_quirk is used only in host.c file.
We can make it as static and removes it from host-export.h.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>