staging: vt6655: remove redundant assignment of pointer tx_key

Pointer tx_key is being assigned a value that is never read, it is
being re-assigned a new value later. The assignment is redundant
and can be removed.

Cleans up clan scan build warning:
drivers/staging/vt6655/rxtx.c:1311:3: warning: Value stored
to 'tx_key' is never read [deadcode.DeadStores]
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220307143625.136189-1-colin.i.king@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6655/rxtx.c

@@ -1308,8 +1308,6 @@ int vnt_generate_fifo_header(struct vnt_private *priv, u32 dma_idx,
 			cpu_to_le16(ieee80211_get_hdrlen_from_skb(skb) << 10);
 
 	if (info->control.hw_key) {
-		tx_key = info->control.hw_key;
-
 		switch (info->control.hw_key->cipher) {
 		case WLAN_CIPHER_SUITE_WEP40:
 		case WLAN_CIPHER_SUITE_WEP104: