Revert "iommu/iova: increase the iova_rcache depot max size to 128"

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8KS9A


CVE: NA

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This reverts commit 0227a749.

Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>