crypto: sha512 - use standard ror64()

Use standard ror64() instead of hand-written.
There is no standard ror64, so create it.

The difference is shift value being "unsigned int" instead of uint64_t
(for which there is no reason). gcc starts to emit native ROR instructions
which it doesn't do for some reason currently. This should make the code
faster.

Patch survives in-tree crypto test and ping flood with hmac(sha512) on.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>