aoe: remove unnecessary mutex_init()

The mutex ktio_spawn_lock is initialized statically.
It is unnecessary to initialize by mutex_init().

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20210511113440.3772053-1-yangyingliang@huawei.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>