md: Don't clear MD_CLOSING until mddev is freed

md: Don't clear MD_CLOSING until mddev is freed

UNTIL_STOP is used to avoid mddev is freed on the last close before adding
disks to mddev. And it should be cleared when stopping an array which is
mentioned in commit efeb53c0e572 ("md: Allow md devices to be created by
name."). So reset ->hold_active to 0 in md_clean.

And MD_CLOSING should be kept until mddev is freed to avoid reopen.

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Xiao Ni <xni@redhat.com>
Link: https://lore.kernel.org/linux-raid/20250611073108.25463-3-xni@redhat.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>