pseries: Remove unneeded include statement (fixes MinGW builds)

sys/mman.h is not needed (tested on Linux) and unavailable for MinGW,
so remove it.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

hw/spapr_nvram.c

@@ -21,7 +21,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-#include <sys/mman.h>
+
 #include <libfdt.h>
 
 #include "sysemu/device_tree.h"