platform/x86: thinkpad_acpi: not loading brightness_init when _BCL invalid

When _BCL invalid, disable thinkpad_acpi backlight brightness control.

brightness_enable is already checked at the beginning.
Most new thinkpads are using GPU driver to control brightness now,
print notice when enabled brightness control even when brightness_enable = 1.
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -6963,10 +6963,13 @@ static int __init brightness_init(struct ibm_init_struct *iibm)
 			pr_warn("Cannot enable backlight brightness support, ACPI is already handling it.  Refer to the acpi_backlight kernel parameter.\n");
 			return 1;
 		}
-	} else if (tp_features.bright_acpimode && brightness_enable > 1) {
-		pr_notice("Standard ACPI backlight interface not available, thinkpad_acpi native brightness control enabled\n");
+	} else if (!tp_features.bright_acpimode) {
+		pr_notice("ACPI backlight interface not available\n");
+		return 1;
 	}
 
+	pr_notice("ACPI native brightness control enabled\n");
+
 	/*
 	 * Check for module parameter bogosity, note that we
 	 * init brightness_mode to TPACPI_BRGHT_MODE_MAX in order to be