ACPI: do not warn if _BQC does not exist

Starting from ACPI spec 3.0, it's only clarified that _BCM control
method is required if _BCL is implemented. There is no word
saying _BQC is required.

And in ACPI spec 6.1 B.5.4, for _BQC, it is explicitly stated that
"This optional method returns the current brightness level of a
built-in display output device. If present, it must be set by
the platform for initial brightness."

Thus remove the obsolete warning message.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/scan.c

@@ -1119,9 +1119,6 @@ acpi_backlight_cap_match(acpi_handle handle, u32 level, void *context,
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found generic backlight "
 				  "support\n"));
 		*cap |= ACPI_VIDEO_BACKLIGHT;
-		if (!acpi_has_method(handle, "_BQC"))
-			printk(KERN_WARNING FW_BUG PREFIX "No _BQC method, "
-				"cannot determine initial brightness\n");
 		/* We have backlight support, no need to scan further */
 		return AE_CTRL_TERMINATE;
 	}