Switch EVP_PKEY_dup calls to EVP_PKEY_up_ref.

Keep internal callers up-to-date with deprecations.

Change-Id: I7ee171afc669592d170f83bd4064857d59332878
Reviewed-on: https://boringssl-review.googlesource.com/4640
Reviewed-by: Adam Langley <agl@google.com>

ssl/ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index a6d2587..6c8e2c9 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -353,7 +353,8 @@
 
   s->tlsext_channel_id_enabled = ctx->tlsext_channel_id_enabled;
   if (ctx->tlsext_channel_id_private) {
-    s->tlsext_channel_id_private = EVP_PKEY_dup(ctx->tlsext_channel_id_private);
+    s->tlsext_channel_id_private =
+        EVP_PKEY_up_ref(ctx->tlsext_channel_id_private);
   }
 
   s->signed_cert_timestamps_enabled = s->ctx->signed_cert_timestamps_enabled;