disas/arm-a64.cc: Include osdep.h first

Rearrange include directives so that we include osdep.h first.
This has to be done manually because clean-includes doesn't
handle C++.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>

disas/arm-a64.cc

@@ -17,12 +17,13 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "vixl/a64/disasm-a64.h"
-
 extern "C" {
+#include "qemu/osdep.h"
 #include "disas/bfd.h"
 }
 
+#include "vixl/a64/disasm-a64.h"
+
 using namespace vixl;
 
 static Decoder *vixl_decoder = NULL;