xfs: set minleft correctly for randomly sparse inode allocations

hulk inclusion
category: bugfix
bugzilla: 188788, https://gitee.com/openeuler/kernel/issues/I76JSK


CVE: NA

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In DEBUG mode may do sparse inode allocations randomly, but forget to
set the remaining space correctly for the inode btree to split.
It's OK for most cases, only under DEBUG mode and AG space is running
out may bring something bad.

Fixes: 1cdadee1 ("xfs: randomly do sparse inode allocations in DEBUG mode")
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Signed-off-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Long Li <leo.lilong@huawei.com>