Revert "writeback: Avoid iput() from flusher thread"

This reverts commit 2fc57e11e801725ce1aaa983d6bb336a8a0dab53.
Revert "vfs: Rename end_writeback() to clear_inode()"

This reverts commit 5c29694f6a641e9d5a9b064e44b6e047001e0277.
Revert "vfs: Move waiting for inode writeback from end_writeback() to evict_inode()"

This reverts commit 01513f7e3f0d3dd3a3087fe4b5369a9feeec290c.
Revert "writeback: Refactor writeback_single_inode()"

This reverts commit c2fa2e598ee16109d6739f7660cc6880715b5f37.