ACPI: Split out custom_method functionality into an own driver

With /sys/kernel/debug/acpi/custom_method root can write
to arbitrary memory and increase his priveleges, even if
these are restricted.

-> Make this an own debug .config option and warn about the
security issue in the config description.

-> Still keep acpi/debugfs.c which now only creates an empty
   /sys/kernel/debug/acpi directory. There might be other
   users of it later.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: rui.zhang@intel.com
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index d113fa5..cba0b23 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -62,6 +62,7 @@
 obj-$(CONFIG_ACPI_POWER_METER)	+= power_meter.o
 obj-$(CONFIG_ACPI_HED)		+= hed.o
 obj-$(CONFIG_ACPI_EC_DEBUGFS)	+= ec_sys.o
+obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
 
 # processor has its own "processor." module_param namespace
 processor-y			:= processor_driver.o processor_throttling.o