wifi: lib80211: remove unused variables iv32 and iv16

clang with W=1 reports
net/wireless/lib80211_crypt_tkip.c:667:7: error: variable 'iv32'
  set but not used [-Werror,-Wunused-but-set-variable]
                u32 iv32 = tkey->tx_iv32;
                    ^
This variable not used so remove it.
Then remove a similar iv16 variable.
Change the comment because the unmodified value is returned.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230517123310.873023-1-trix@redhat.com
[change commit log wrt. 'length', add comment in the code]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/lib80211_crypt_tkip.c

@@ -662,12 +662,12 @@ static int lib80211_tkip_get_key(void *key, int len, u8 * seq, void *priv)
 	memcpy(key, tkey->key, TKIP_KEY_LEN);
 
 	if (seq) {
-		/* Return the sequence number of the last transmitted frame. */
-		u16 iv16 = tkey->tx_iv16;
-		u32 iv32 = tkey->tx_iv32;
-		if (iv16 == 0)
-			iv32--;
-		iv16--;
+		/*
+		 * Not clear if this should return the value as is
+		 * or - as the code previously seemed to partially
+		 * have been written as - subtract one from it. It
+		 * was working this way for a long time so leave it.
+		 */
 		seq[0] = tkey->tx_iv16;
 		seq[1] = tkey->tx_iv16 >> 8;
 		seq[2] = tkey->tx_iv32;