Fix compile failure

Fix compile failure introduced by commit 94d61512360c due to a typo.

Reviewed-by: Richard Levitte <levitte@openssl.org>

ssl/s3_lib.c

diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index ee00741..c08065f 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -4466,7 +4466,7 @@
 #ifndef OPENSSL_NO_DH
     case SSL_CTRL_SET_TMP_DH_CB:
         {
-            cxt->cert->dh_tmp_cb = (DH *(*)(SSL *, int, int))fp;
+            ctx->cert->dh_tmp_cb = (DH *(*)(SSL *, int, int))fp;
         }
         break;
 #endif