fs: add read_iter and write_iter to several file systems

fs: add read_iter and write_iter to several file systems

These are the simple ones.

File systems that use generic_file_aio_read() and generic_file_aio_write()
can trivially support generic_file_read_iter() and generic_file_write_iter().

This patch adds those file_operations for 9p, adfs, affs, bfs, exofs, ext2,
ext3, fat, f2fs, hfs, hfsplus, hostfs, hpfs, jfs, jffs2, logfs, minix, nilfs2,
omfs, ramfs, reiserfs, romfs, sysv, and ufs.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Boaz Harrosh <bharrosh@panasas.com>
Cc: Zach Brown <zab@zabbo.net>