Removed duplicate initialization of the "rev" variable.

src/os/unix/ngx_readv_chain.c

diff --git a/src/os/unix/ngx_readv_chain.c b/src/os/unix/ngx_readv_chain.c
index 8523be3..3cba80c 100644
--- a/src/os/unix/ngx_readv_chain.c
+++ b/src/os/unix/ngx_readv_chain.c
@@ -91,8 +91,6 @@
     ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
                    "readv: %d, last:%d", vec.nelts, iov->iov_len);
 
-    rev = c->read;
-
     do {
         n = readv(c->fd, (struct iovec *) vec.elts, vec.nelts);