crypto: marvell - make mv_cesa_ahash_cache_req() return bool

The mv_cesa_ahash_cache_req() function always returns 0, which makes
its return value pretty much useless. However, in addition to
returning a useless value, it also returns a boolean in a variable
passed by reference to indicate if the request was already cached.

So, this commit changes mv_cesa_ahash_cache_req() to return this
boolean. It consequently simplifies the only call site of
mv_cesa_ahash_cache_req(), where the "ret" variable is no longer
needed.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>