staging/lustre/llite: Update all file.c user pointer casts to __user

unsigned long user address must be casted with __user attribute
to make sparse happy when used with userspace access functions.

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