Wire up generic_file_splice_read for the iter based proxy ops, so
that splice reads from them work.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>