net: marvell: prestera: add missing destroy_workqueue() in prestera_module_init()

Add the missing destroy_workqueue() before return from
prestera_module_init() in the error handling case.

Fixes: 4394fbcb

 ("net: marvell: prestera: handle fib notifications")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220322090236.1439649-1-yangyingliang@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>