drm/i915: Move out engine related macros from i915_drv.h

Move macros related to engines out of i915_drv.h header and
place them in intel_engine.h.

Signed-off-by: Krzysztof Karas <krzysztof.karas@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/9b9ed5bbdb37470fa679c5baf961424c9cfbad11.1750251040.git.krzysztof.karas@intel.com