Staging: wilc1000: Freed memory in case of error

This patch frees memory allocated inside wilc_wlan_txq_add_cfg_pkt()
in case wilc_wlan_txq_add_to_head() fails.

Signed-off-by: Claudiu Beznea <claudiu.beznea@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>