Staging: w35und: plug memory leak in wbsoft_tx()

There's no reason to duplicate the skb in wbsoft_tx() and leak GFP_ATOMIC
memory as the contents are copied to ->TxBuffer in MdxTx() anyway before
MLMESendFrame() returns.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>