bfqio: Add missing include header

Change-Id: I50851e633c54cd0e2e37789e88a226aaa80e8c2c

libbfqio/bfqio.c

@@ -21,6 +21,7 @@
 #include <cutils/log.h>
 #include <pthread.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 static int __rtio_cgroup_supported = -1;
 static pthread_once_t __rtio_init_once = PTHREAD_ONCE_INIT;