tap: Compilation fix for Solaris

Avoid an unresolved symbol error for TFR,
which is defined in sysemu.h.

Based on patch by Palle Lyckegaard.

Signed-off-by: Andreas Färber <afaerber@opensolaris.org>
Cc: Palle Lyckegaard <palle@lyckegaard.dk>
Cc: Ben Taylor <bentaylor.solx86@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

net/tap-solaris.c

@@ -23,6 +23,7 @@
  */
 
 #include "net/tap.h"
+#include "sysemu.h"
 
 #include <sys/stat.h>
 #include <sys/ethernet.h>