crypto: qat - validate service in rate limiting sysfs api

The sysfs interface 'qat_rl/srv' currently allows all valid services,
even if a service is not configured for the device. This leads to a failure
when attempting to add the SLA using 'qat_rl/sla_op'.

Add a check using is_service_enabled() to ensure the requested service is
enabled. If not, return -EINVAL to prevent invalid configurations.

Signed-off-by: Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>