Other than internal api get_bitmap_from_slot(), all other places will
set returned bitmap to mddev->bitmap. So move the setting of
mddev->bitmap into md_bitmap_create() to simplify code.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-13-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>