wusb: delete double assignment

Delete successive assignments to the same location.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression i;
@@

*i = ...;
 i = ...;
// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/wusbcore/crypto.c

@@ -222,8 +222,6 @@ static int wusb_ccm_mac(struct crypto_blkcipher *tfm_cbc,
 	WARN_ON(sizeof(ax) != sizeof(struct aes_ccm_block));
 
 	result = -ENOMEM;
-	zero_padding = sizeof(struct aes_ccm_block)
-		- blen % sizeof(struct aes_ccm_block);
 	zero_padding = blen % sizeof(struct aes_ccm_block);
 	if (zero_padding)
 		zero_padding = sizeof(struct aes_ccm_block) - zero_padding;