drm/i915/gvt: Return -EIO if host enable_execlists not enabled when loading GVT-g

GVT-g relies on the enable_execlists parameter in i915. If this option
is not enabled for GVT-g, should return -EIO to make i915 driver loading
failed.

v2:
- Use DMR_ERROR as it is a fatal message. (Chris)

Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/intel_gvt.c

@@ -96,8 +96,8 @@ int intel_gvt_init(struct drm_i915_private *dev_priv)
 	}
 
 	if (!i915.enable_execlists) {
-		DRM_INFO("GPU guest virtualisation [GVT-g] disabled due to disabled execlist submission [i915.enable_execlists module parameter]\n");
-		goto bail;
+		DRM_ERROR("i915 GVT-g loading failed due to disabled execlists mode\n");
+		return -EIO;
 	}
 
 	/*