staging: lustre: Replace sscanf with kstrtoint

Replace single variable sscanf with specialized function
kstrtoint at the suggestion of checkpatch.pl, to fix
'WARNING: Prefer kstrto<type> to single variable sscanf'

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>