block: Only set bb->changed when badblocks changes

hulk inclusion
category: bugfix
bugzilla: 188569, https://gitee.com/openeuler/kernel/issues/I6ZG5B


CVE: NA

--------------------------------

bb->changed and unacked_exist is set and badblocks_update_acked() is
involked even if no badblocks changes in badblocks_set(). Only update
them when badblocks changes.

Fixes: 9e0e252a ("badblocks: Add core badblock management code")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>