drm/i915: Split GPU commands definitions into separate header

We should not mix MMIO with MI_INSTR definitions.

v2: sanitize comment, change include order (Chris)
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180313124109.39216-1-michal.wajdeczko@intel.com
Link: https://patchwork.freedesktop.org/patch/msgid/20180313231920.6932-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -7,10 +7,11 @@
 #include "i915_gem_batch_pool.h"
 #include "i915_gem_timeline.h"
 
-#include "i915_reg.h" /* FIXME split out i915_gpu_commands.h */
+#include "i915_reg.h"
 #include "i915_pmu.h"
 #include "i915_request.h"
 #include "i915_selftest.h"
+#include "intel_gpu_commands.h"
 
 struct drm_printer;