crypto: hisilicon - Fixed some tiny bugs of HPRE

1.Use memzero_explicit to clear key;
2.Fix some little endian writings;
3.Fix some other bugs and stuff of code style;

Signed-off-by: Zaibo Xu <xuzaibo@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>