crypto: hisilicon/sec - add some comments for soft fallback

mainline inclusion
from mainline-crypto-master
commit e764d81d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4WC3O


CVE: NA

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Modify the print of information that might lead to user misunderstanding.
Currently only XTS mode need the fallback tfm when using 192bit key.
Others algs not need soft fallback tfm. So others algs can return
directly.

Signed-off-by: Kai Ye <yekai13@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>