crypto: marvell/cesa - add flag to determine algorithm endianness

Rather than determining whether we're using a MD5 hash by looking at
the digest size, switch to a cleaner solution using a per-request flag
initialised by the method type.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>