xfs: factor out __xfs_da3_node_read()

Offering: HULK
hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I76JSK



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Factor out a wrapper __xfs_da3_node_read() from xfs_da3_node_read()
which could pass flags parameter.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Long Li <leo.lilong@huawei.com>