Save the string address before pass to strsep, release it at end.
Because strsep will update the string address to point after the
token.

Fixes: c31dc9fe("crypto: hisilicon/qm - add DebugFS for xQC and...")
Signed-off-by: Sihang Chen <chensihang1@hisilicon.com>
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Reviewed-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>