ACPI: thermal: create "thermal.off=1" to disable ACPI thermal support

"thermal.off=1" disables all ACPI thermal support at boot time.

CONFIG_ACPI_THERMAL=n can do this at build time.
"# rmmod thermal" can do this at run time,
as long as thermal is built as a module.

WARNING: On some systems, disabling ACPI thermal support
will cause the system to run hotter and reduce the
lifetime of the hardware.

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