usb: use local path for local headers

When pulling in headers that are in the same directory as the C file (as
opposed to one in include/), we should use its relative path, without a
directory.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
diff --git a/hw/usb/dev-network.c b/hw/usb/dev-network.c
index aea7edc..385e090 100644
--- a/hw/usb/dev-network.c
+++ b/hw/usb/dev-network.c
@@ -27,7 +27,7 @@
 #include "qapi/error.h"
 #include "qemu-common.h"
 #include "hw/usb.h"
-#include "hw/usb/desc.h"
+#include "desc.h"
 #include "net/net.h"
 #include "qemu/error-report.h"
 #include "qemu/queue.h"