ACPI: thermal: create "thermal.crt=C" bootparam

Some hardware will malfunction at a temperature below
the BIOS provided critical shutdown threshold.

This hook allows moving the critical trip points down
to a temperature which provokes a graceful shutdown
before the hardware malfunction.

http://bugzilla.kernel.org/show_bug.cgi?id=8884

WARNING: A trip-point override will not get noticed
until the system delivers a temperature change event,
or unless thermal zone polling is enabled.
eg. "thermal.tzp=10"

Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/kernel-parameters.txt

@@ -1826,6 +1826,10 @@ and is between 256 and 4096 characters. It is defined in the file
 			-1: disable all active trip points in all thermal zones
 			<degrees C>: override all lowest active trip points
 
+	thermal.crt=	[HW,ACPI]
+			-1: disable all critical trip points in all thermal zones
+			<degrees C>: lower all critical trip points
+
 	thermal.nocrt=	[HW,ACPI]
 			Set to disable actions on ACPI thermal zone
 			critical and hot trip points.