devm_kstrdup() returns pointer to allocated string on success, NULL on
failure. So it is better to check the return value of it.

Link: https://lore.kernel.org/r/tencent_4257E15D4A94FF9020DDCC4BB9B21C041408@qq.comReviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>