Revert "tmpfs: add support for read_iter and write_iter"

This reverts commit e255cf5d4d5953b7be1d5908b087211f2803f095.
Revert "iov_iter: move into its own file (bug fix)"

This reverts commit ec26238d1fbc31818fef059f2afa0b16c8cecf6c.
Revert "ecrpytfs: Convert aio_read/write ops to read/write_iter"

This reverts commit d635e822c8a65acb16e712249add4be755fd27ea.
Revert "ext4: add support for read_iter and write_iter"

This reverts commit a14be5431a46ae1a751f2582b2e4e8e16759a5b1.