qga: cast to int for DWORD type

This patch fixes a compiler warning when cross-build:

qga/service-win32.c: In function 'printf_win_error':
qga/service-win32.c:32:5: warning: format '%d' expects argument of type 'int',
                          but argument 3 has type 'DWORD' [-Wformat]
Signed-off-by: NLei Li <lilei@linux.vnet.ibm.com>
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

qga/service-win32.c

@@ -29,7 +29,7 @@ static int printf_win_error(const char *text)
         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
         (char *)&message, 0,
         NULL);
-    n = printf("%s. (Error: %d) %s", text, err, message);
+    n = printf("%s. (Error: %d) %s", text, (int)err, message);
     LocalFree(message);
 
     return n;