Fix build error for aarch64 big endian.

Modified rev to rev64, because rev only takes integer registers.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90827
Otherwise, the following error will occur.

Error: operand 1 must be an integer register -- `rev v31.16b,v31.16b'

CLA: trivial

Signed-off-by: Lei Maohui <leimaohui@cn.fujitsu.com>

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9151)
