Revert "tmpfs: add support for read_iter and write_iter"

This reverts commit 8b891104ccc424dca212f8a664f7f2f90443011a.
Revert "fs: pull iov_iter use higher up the stack"

This reverts commit eb0d230987624631e6c4dfacef7330ac88aa85b8.
Revert "dio: Convert direct_IO to use iov_iter"

This reverts commit 9573288d126794dbd7474374575103238a2482f9.
Revert "iov_iter: move into its own file"

This reverts commit 15e6fa73073be19512faaa8b317a3c56aa4d1635.
Revert "f2fs:data: add AIO optimization"

This reverts commit a3e627344647c7630f961f5059f2f6756a125b7d.
Revert "f2fs:data: add AIO optimization"

This reverts commit 40bf49c8813ec10d542010b64658f4b47d58111f.
Revert "exfat: AIO Optimization compatibility fixup"

This reverts commit 02219e15cd28b0f277861f8b403ec2e7ab118fe3.