[Lenovo x240] acpi_throttle fails to attach

[Sean Bruno]

x240 dsdt -->
http://people.freebsd.org/~sbruno/acpi_dump_lenovo_x240.dsdt

It sort of looks like we havn't implemented something for newer haswell
cpus yet?

acpi_throttle0: <ACPI CPU Throttling> on cpu0
est0: <Enhanced SpeedStep Frequency Control> on cpu0
acpi_throttle1: <ACPI CPU Throttling> on cpu1
acpi_throttle1: failed to attach P_CNT
device_attach: acpi_throttle1 attach returned 6
est1: <Enhanced SpeedStep Frequency Control> on cpu1
acpi_throttle2: <ACPI CPU Throttling> on cpu2
acpi_throttle2: failed to attach P_CNT
device_attach: acpi_throttle2 attach returned 6
est2: <Enhanced SpeedStep Frequency Control> on cpu2
acpi_throttle3: <ACPI CPU Throttling> on cpu3
acpi_throttle3: failed to attach P_CNT
device_attach: acpi_throttle3 attach returned 6
est3: <Enhanced SpeedStep Frequency Control> on cpu3