acpi: thermal: display forced passive trip points in proc

Users can force a passive trip point for a thermal zone that does not have
_PSV defined in ACPI by setting the passive attribute in sysfs.  It's
useful to display such trip points in /proc/acpi/thermal_zone.

.../TZ1/cooling_mode:<setting not supported>
.../TZ1/polling_frequency:polling frequency:       10 seconds
.../TZ1/state:state:                   ok
.../TZ1/temperature:temperature:             53 C
.../TZ1/trip_points:critical (S5):           110 C
.../TZ1/trip_points:passive (forced):        95 C

And if not set (passive is 0):
.../TZ1/trip_points:passive (forced):<not set>

Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>