usb: Fix bootindex for portnr > 9

We identify devices by their Open Firmware device paths.  The encoding
of the host controller and hub port numbers is incorrect:
usb_get_fw_dev_path() formats them in decimal, while SeaBIOS uses
hexadecimal.  When some port number > 9, SeaBIOS will miss the
bootindex (lucky case), or apply it to another device (unlucky case).

The relevant spec[*] agrees with SeaBIOS (and OVMF, for that matter).
Change %d to %x.

Bug can bite only with host controllers or hubs sporting more than ten
ports.  I'm not aware of any.

[*] Open Firmware Recommended Practice: Universal Serial Bus,
Version 1, Section 3.2.1 Device Node Address Representation
http://www.openfirmware.org/1275/bindings/usb/usb-1_0.psSigned-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>

Note: xhci can be configured with up to 15 ports (default is 4 ports).
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/bus.c

@@ -589,11 +589,11 @@ static char *usb_get_fw_dev_path(DeviceState *qdev)
         nr = strtol(in, &in, 10);
         if (in[0] == '.') {
             /* some hub between root port and device */
-            pos += snprintf(fw_path + pos, fw_len - pos, "hub@%ld/", nr);
+            pos += snprintf(fw_path + pos, fw_len - pos, "hub@%lx/", nr);
             in++;
         } else {
             /* the device itself */
-            pos += snprintf(fw_path + pos, fw_len - pos, "%s@%ld",
+            pos += snprintf(fw_path + pos, fw_len - pos, "%s@%lx",
                             qdev_fw_name(qdev), nr);
             break;
         }