ext2: remove ext2_new_block()

hulk inclusion
category: feature
bugzilla: 189105, https://gitee.com/openeuler/kernel/issues/I7TN3J



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Now, only xattr allocate block use ext2_new_block(), so just opencode it in
the xattr code.

Signed-off-by: Ye Bin <yebin10@huawei.com>