md: use new apis to suspend array for adding/removing rdev from state_store()

User can write 'remove' and 're-add' to trigger array reconfiguration
through sysfs, suspend array in this case so that io won't concurrent
with array reconfiguration.

And now that all the caller of add_bound_rdev() alread suspend the
array, remove mddev_suspend/resume() from add_bound_rdev() as well.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231010151958.145896-12-yukuai1@huaweicloud.com