ehci-sysbus: Attach DMA context.

This was left as NULL on the initial merge due to debate on the mailing list on
how to handle DMA contexts for sysbus devices. Patch
9e11908f was later merged to fix OHCI. This is the,
equivalent fix for sysbus EHCI.
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ehci-sysbus.c

@@ -45,6 +45,7 @@ static int usb_ehci_sysbus_initfn(SysBusDevice *dev)
 
     s->capsbase = 0x100;
     s->opregbase = 0x140;
+    s->dma = &dma_context_memory;
 
     usb_ehci_initfn(s, DEVICE(dev));
     sysbus_init_irq(dev, &s->irq);