service: use id in get by name function

service: use id in get by name function

This commit reworks the service_get_by_name() function to
accept an integer, and removes the service_get_by_id() function.

All functions now accept an integer argument representing the
service, so it is no longer required to expose the service_spec
pointers to the application.

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>