staging/lustre/llite: move llite/max_read_ahead_per_file_mb to sysfs

Move max_read_ahead_per_file_mb file from /proc/fs/lustre/llite/*
to /sys/fs/lustre/llite/*/

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>