ktls_send_ctrl_message(): Fix parameter name from 'lengthi' to 'length'

In include/internal/ktls.h, the variable/parameter lengthi is used
in Kernel TLS (KTLS) helper declarations and macros, whereas all
related functions across the codebase consistently use length.

This naming inconsistency triggers static analysis warnings
(including potential CWE-467 flags regarding parameter/pointer
evaluation in macro expansions) and creates confusion during maintenance.
The identifier lengthi appears to be an unintended typo introduced
during the original KTLS interface definition.

CLA: trivial
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Norbert Pocs <norbertp@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Merge-date: Mon Sep  7 18:42:31 2026
Merged-from: https://github.com/openssl/openssl/pull/32568