ACPI: thermal: Drop redundant local variable from acpi_thermal_resume()

Commit dabc621a ("ACPI: thermal: Drop enabled flag from struct
acpi_thermal_active") left behind a variable that is only assigned to
and never read, so drop it now.

Fixes: dabc621a ("ACPI: thermal: Drop enabled flag from struct acpi_thermal_active")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>