Fix a man page typo

The man page line of 'fadvise_hit' is exactly opposite to its true meaning.

Signed-off-by: Zhu Yanhai <gaoyang.zyh@taobao.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.1 b/fio.1
index aeba39a..75c8ec6 100644
--- a/fio.1
+++ b/fio.1
@@ -281,7 +281,7 @@
 .RE
 .TP
 .BI fadvise_hint \fR=\fPbool
-Disable use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns
+Use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns
 are likely to be issued. Default: true.
 .TP
 .BI size \fR=\fPint