This patch adds the basic definitions needed to support
new copy engines. Also updating the cmd_info to accommodate
new engines, as the engine id's of legacy engines have been
changed.
v2:
- Add _BCS(n) definition, similar to other engines. (Tvrtko)
- Add I915_MAX_BCS definition, similar to other engnes. (Prathap)
- Move GVT change to avoid u16 overflow to its own patch. (Tvrtko)