hw/i386: Fix broken build for non POSIX hosts

pc-testdev.c cannot be compiled with MinGW (and other non POSIX hosts):

  CC    i386-softmmu/hw/i386/../pc-testdev.o
qemu/hw/i386/../pc-testdev.c:38:22: warning: sys/mman.h: file not found
qemu/hw/i386/../pc-testdev.c: In function ‘test_flush_page’:
qemu/hw/i386/../pc-testdev.c:103: warning: implicit declaration of function ‘mprotect’
...

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/pc-testdev.c b/hw/pc-testdev.c
index 620c86c..1928489 100644
--- a/hw/pc-testdev.c
+++ b/hw/pc-testdev.c
@@ -35,7 +35,10 @@
  * git://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git
 */
 
+#include "config-host.h"
+#if defined(CONFIG_POSIX)
 #include <sys/mman.h>
+#endif
 #include "hw.h"
 #include "qdev.h"
 #include "isa.h"
@@ -100,8 +103,10 @@
 
     /* We might not be able to get the full page, only mprotect what we actually
        have mapped */
+#if defined(CONFIG_POSIX)
     mprotect(a, page, PROT_NONE);
     mprotect(a, page, PROT_READ|PROT_WRITE);
+#endif
     cpu_physical_memory_unmap(a, page, 0, 0);
 }