drm/i915/tgl: the BCS engine supports relative MMIO

The specs don't mention any specific HW limitation on the blitter and
manual inspection shows that the HW does set the relative MMIO bit in
the LRI of the blitter context image, so we can remove our limitations.
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
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/20191009230424.6507-1-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -3451,7 +3451,7 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 			engine->flags |= I915_ENGINE_HAS_PREEMPTION;
 	}
 
-	if (engine->class != COPY_ENGINE_CLASS && INTEL_GEN(engine->i915) >= 12)
+	if (INTEL_GEN(engine->i915) >= 12)
 		engine->flags |= I915_ENGINE_HAS_RELATIVE_MMIO;
 }