vhost: move stdbool include

The vhost.h file uses bool type, but not include stdbool
header file. If other c files include vhost.h directly,
there will be a compile error.

This patch will be used in the next patch.

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

lib/librte_vhost/socket.c

@@ -4,7 +4,6 @@
 
 #include <stdint.h>
 #include <stdio.h>
-#include <stdbool.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <unistd.h>

lib/librte_vhost/vhost.h

@@ -6,6 +6,7 @@
 #define _VHOST_NET_CDEV_H_
 #include <stdint.h>
 #include <stdio.h>
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/queue.h>
 #include <unistd.h>