drm/i915: remove ACPI related DRM_ERRORs

They're not really errors (well actually I don't know; I don't
understand _DSM and _MUX well enough to say, but I do know they spam
people's logs and seem to be harmless).

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: The _DSM error got remove in another patch already]
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44250
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_acpi.c

@@ -182,8 +182,6 @@ static void intel_dsm_platform_mux_info(void)
 			DRM_DEBUG_DRIVER("  hpd mux info: %s\n",
 			       intel_dsm_mux_type(info->buffer.pointer[3]));
 		}
-	} else {
-		DRM_ERROR("MUX INFO call failed\n");
 	}
 
 out: