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>