Fix BSD and win32 builds

CC    net/tap-bsd.o
/src/qemu/net/tap-bsd.c: In function `tap_open':
/src/qemu/net/tap-bsd.c:93: warning: implicit declaration of function `error_report'

  CC    sparc-softmmu/../net/tap-win32.o
cc1: warnings being treated as errors
/src/qemu/target-sparc/../net/tap-win32.c: In function 'net_init_tap':
/src/qemu/target-sparc/../net/tap-win32.c:709: warning: implicit declaration of function 'error_report'

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

net/tap-bsd.c

@@ -25,6 +25,7 @@
 #include "net/tap.h"
 #include "qemu-common.h"
 #include "sysemu.h"
+#include "qemu-error.h"
 
 #ifdef __NetBSD__
 #include <net/if_tap.h>

net/tap-win32.c

@@ -31,6 +31,7 @@
 #include "qemu-common.h"
 #include "net.h"
 #include "sysemu.h"
+#include "qemu-error.h"
 #include <stdio.h>
 #include <windows.h>
 #include <winioctl.h>