staging: lustre: llite: Replace the symbolic file permission mode with the numeric one

Replaces S_IRWXUGO with 0777. The reason is that symbolic permissions
considered harmful:
https://lwn.net/Articles/696229/



Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>