[openssl/openssl] ca0dd5: Remove redundant assignment in felem_mul_ref in p521

[openssl-machine]

  Branch: refs/heads/openssl-3.1
  Home:   https://github.com/openssl/openssl
  Commit: ca0dd5f4a303def58800a7e4d7edf9242ed73241
      https://github.com/openssl/openssl/commit/ca0dd5f4a303def58800a7e4d7edf9242ed73241
  Author: Rohan McLure <rohanmclure at linux.ibm.com>
  Date:   2022-11-30 (Wed, 30 Nov 2022)

  Changed paths:
    M crypto/ec/ecp_nistp521.c

  Log Message:
  -----------
  Remove redundant assignment in felem_mul_ref in p521

ftmp4 is assigned immediately before receiving the reduced output of the
multiplication of ftmp and ftmp3, without being read inbetween these
assignments. Remove redundant assignment.

Reviewed-by: Hugo Landau <hlandau at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19766)

(cherry picked from commit 3d4dfeb28a5cb944b8300b4cf807e19ab97d04f5)