mm/filemap: Pass the file_ra_state in the ractl

mm/filemap: Pass the file_ra_state in the ractl

For readahead_expand(), we need to modify the file ra_state, so pass it
down by adding it to the ractl.  We have to do this because it's not always
the same as f_ra in the struct file that is already being passed.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20210407201857.3582797-2-willy@infradead.org/