PKCS#7: drop function from kernel-doc pkcs7_validate_trust_one

PKCS#7: drop function from kernel-doc pkcs7_validate_trust_one

The function is a static function, so no needs add into kernel-doc. and
we could avoid warning:
crypto/asymmetric_keys/pkcs7_trust.c:25: warning: Function parameter or
member 'pkcs7' not described in 'pkcs7_validate_trust_one'
crypto/asymmetric_keys/pkcs7_trust.c:25: warning: Function parameter or
member 'sinfo' not described in 'pkcs7_validate_trust_one'
crypto/asymmetric_keys/pkcs7_trust.c:25: warning: Function parameter or
member 'trust_keyring' not described in 'pkcs7_validate_trust_one'

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ben Boeckel <mathstuf@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: keyrings@vger.kernel.org
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org