staging: lustre: lustre: llite: Use kstrdup

Use kstrdup when the goal of an allocation is copy a string into the
allocated region.

Patch found by coccicheck.

Signed-off-by: Tapasweni Pathak <tapaswenipathak@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>