md: do not require mddev_lock() for all options in array_state_store()

We don't need to lock device to reject not supported request
in array_state_store(). No functional changes intended.

There are differences between ioctl and sysfs handling during stopping.
With this change, it will be easier to add additional steps which needs
to be completed before mddev_lock() is taken.

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230928125517.12356-1-mariusz.tkaczyk@linux.intel.com