md/raid1-10: submit write io directly if bitmap is not enabled

mainline inclusion
from mainline-v6.5-rc1
commit 7db922ba
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I8UKFJ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7db922bae3abdf0a1db81ef7228cc0b996a0c1e3



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Commit 6cce3b23 ("[PATCH] md: write intent bitmap support for raid10")
add bitmap support, and it changed that write io is submitted through
daemon thread because bitmap need to be updated before write io. And
later, plug is used to fix performance regression because all the write io
will go to demon thread, which means io can't be issued concurrently.

However, if bitmap is not enabled, the write io should not go to daemon
thread in the first place, and plug is not needed as well.

Fixes: 6cce3b23 ("[PATCH] md: write intent bitmap support for raid10")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230529131106.2123367-5-yukuai1@huaweicloud.com


Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>