tests: fix usb-hcd-ehci-test compilation

Fixes commit
e5758de4 ("tests/libqtest: Make
qtest_qmp_device_add/del independent from global_qtest")

and commit
dd210749 ("tests/libqtest: Use
libqtest-single.h in tests that require global_qtest").

Cc: Thomas Huth <thuth@redhat.com>
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190926111955.17276-2-marcandre.lureau@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>

tests/usb-hcd-ehci-test.c

@@ -8,7 +8,7 @@
  */
 
 #include "qemu/osdep.h"
-#include "libqtest.h"
+#include "libqtest-single.h"
 #include "libqos/pci-pc.h"
 #include "hw/usb/uhci-regs.h"
 #include "hw/usb/ehci-regs.h"
@@ -139,7 +139,7 @@ static void pci_ehci_port_3_hotplug(void)
 
 static void pci_ehci_port_hotplug(void)
 {
-    usb_test_hotplug("ich9-ehci-1", "3", pci_ehci_port_3_hotplug);
+    usb_test_hotplug(global_qtest, "ich9-ehci-1", "3", pci_ehci_port_3_hotplug);
 }