Fix reallocation failure condition in qtx_resize_txe()

Fix reallocation failure condition in qtx_resize_txe()

Returning the same pointer does not mean that the reallocation failed,
it would also prevent updating alloc_len down below.
This is similar code and a similar change to 043a41ddee.

Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28317)

(cherry picked from commit 220f5be6908631759d56c7a6458be8385d984260)