Make a failure in ktls_sendfile a syscall error

a failure in ktls_sendfile results in an error in ERR_LIB_SSL, but its
really a syscall error, since ktls_sendfile just maps to a call to the
sendfile syscall.  Encode it as such

Fixes #23722

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #23723)

ssl/ssl_lib.c

@@ -2603,7 +2603,8 @@ ossl_ssize_t SSL_sendfile(SSL *s, int fd, off_t offset, size_t size, int flags)
             BIO_set_retry_write(sc->wbio);
         else
 #endif
-            ERR_raise(ERR_LIB_SSL, SSL_R_UNINITIALIZED);
+            ERR_raise_data(ERR_LIB_SYS, get_last_sys_error(),
+                           "ktls_sendfile failure");
         return ret;
     }
     sc->rwstate = SSL_NOTHING;