net/tap-win32: Fix compiler warning caused by missing include statement

The include file for net_init_tap was missing:

net/tap-win32.c:703:
 warning: no previous prototype for ‘net_init_tap’
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

net/tap-win32.c

@@ -29,6 +29,7 @@
 #include "tap.h"
 
 #include "qemu-common.h"
+#include "clients.h"            /* net_init_tap */
 #include "net.h"
 #include "sysemu.h"
 #include "qemu-error.h"