iommu/io-pgtable-arm: Add and realize merge_page ops

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZUKK


CVE: NA

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If block(largepage) mappings are split during start dirty log, then
when stop dirty log, we need to recover them for better DMA performance.

This recovers block mappings and unmap the span of page mappings. BBML1
or BBML2 feature is required.

Merging page is designed to be only used by dirty log tracking, which
does not concurrently work with other pgtable ops that access underlying
page table, so race condition does not exist.

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Reviewed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>