drm/i915: Move intel_engine_mask_t around for use by i915_request_types.h

We want to use intel_engine_mask_t inside i915_request.h, which means
extracting it from the general header file mess and placing it inside a
types.h. A knock on effect is that the compiler wants to warn about
type-contraction of ALL_ENGINES into intel_engine_maskt_t, so prepare
for the worst.

v2: Use intel_engine_mask_t consistently
v3: Move I915_NUM_ENGINES to its natural home at the end of the enum

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190401162641.10963-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/gvt/vgpu.c

@@ -526,11 +526,11 @@ struct intel_vgpu *intel_gvt_create_vgpu(struct intel_gvt *gvt,
  * GPU engines. For FLR, engine_mask is ignored.
  */
 void intel_gvt_reset_vgpu_locked(struct intel_vgpu *vgpu, bool dmlr,
-				 unsigned int engine_mask)
+				 intel_engine_mask_t engine_mask)
 {
 	struct intel_gvt *gvt = vgpu->gvt;
 	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
-	unsigned int resetting_eng = dmlr ? ALL_ENGINES : engine_mask;
+	intel_engine_mask_t resetting_eng = dmlr ? ALL_ENGINES : engine_mask;
 
 	gvt_dbg_core("------------------------------------------\n");
 	gvt_dbg_core("resseting vgpu%d, dmlr %d, engine_mask %08x\n",