os-posix: include sys/mman.h

qemu/osdep.h checks whether MAP_ANONYMOUS is defined, but this check
is bogus without a previous inclusion of sys/mman.h.  Include it in
sysemu/os-posix.h and remove it from everywhere else.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target-s390x/kvm.c

@@ -23,7 +23,6 @@
 
 #include "qemu/osdep.h"
 #include <sys/ioctl.h>
-#include <sys/mman.h>
 
 #include <linux/kvm.h>
 #include <asm/ptrace.h>