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

[ Upstream commit e764d81d ]

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>
Stable-dep-of: fd337f85 ("crypto: hisilicon/sec2 - fix for aead icv error")
Signed-off-by: Sasha Levin <sashal@kernel.org>