ehci: fix port count.

The ICH4 EHCI controller which we emulate has six ports not four.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb-ehci.c

@@ -130,7 +130,7 @@
 #define FRAME_TIMER_NS   (1000000000 / FRAME_TIMER_FREQ)
 
 #define NB_MAXINTRATE    8        // Max rate at which controller issues ints
-#define NB_PORTS         4        // Number of downstream ports
+#define NB_PORTS         6        // Number of downstream ports
 #define BUFF_SIZE        5*4096   // Max bytes to transfer per transaction
 #define MAX_ITERATIONS   20       // Max number of QH before we break the loop
 #define MAX_QH           100      // Max allowable queue heads in a chain