keys: asymmetric: fix error return code in software_key_query()

Fix to return negative error code -ENOMEM from kmalloc() error handling
case instead of 0, as done elsewhere in this function.

Fixes: f1774cb8 ("X.509: parse public key parameters from x509 for akcipher")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>