ACPI / osi: Add acpi_osi=!! to allow reverting acpi_osi=!

This patch introduces acpi_osi=!! so that quirks may use it to revert
acpi_osi=!.

Tested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/kernel-parameters.txt

@@ -312,6 +312,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			acpi_osi=!*		# remove all strings
 			acpi_osi=!		# disable all built-in OS vendor
 						  strings
+			acpi_osi=!!		# enable all built-in OS vendor
+						  strings
 			acpi_osi=		# disable all strings
 
 			'acpi_osi=!' can be used in combination with single or

drivers/acpi/osl.c

@@ -1763,6 +1763,9 @@ void __init acpi_osi_setup(char *str)
 				osi->enable = false;
 			}
 			return;
+		} else if (*str == '!') {
+			osi_config.default_disabling = 0;
+			return;
 		}
 		enable = false;
 	}