The thread to arbiter mapping for 4xxx devices does not allow to
achieve optimal performance for the compression service as it makes
all the engines to compete for the same resources.

Update the logic so that a custom optimal mapping is used for the
compression service.
Signed-off-by: Shashank Gupta <shashank.gupta@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>