SSL: calculation of buffer size moved closer to its usage.

No functional changes.

src/event/ngx_event_openssl.c

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index 362b0f7..c27dba9 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -1207,12 +1207,12 @@
             }
         }
 
-        size = buf->last - buf->pos;
-
         if (!flush && send < limit && buf->last < buf->end) {
             break;
         }
 
+        size = buf->last - buf->pos;
+
         n = ngx_ssl_write(c, buf->pos, size);
 
         if (n == NGX_ERROR) {