acerhdf uses thermal interfaces so it should depend on THERMAL.
It also should not select a thermal driver without checking that
THERMAL is enabled.

This fixes the following build errors when THERMAL=m and
ACERHDF=y.

drivers/built-in.o: In function `acerhdf_set_mode':
acerhdf.c:(.text+0x3e02e1): undefined reference to `thermal_zone_device_update'
drivers/built-in.o: In function `acerhdf_unbind':
acerhdf.c:(.text+0x3e052d): undefined reference to `thermal_zone_unbind_cooling_device'
drivers/built-in.o: In function `acerhdf_bind':
acerhdf.c:(.text+0x3e0593): undefined reference to `thermal_zone_bind_cooling_device'
drivers/built-in.o: In function `acerhdf_init':
acerhdf.c:(.init.text+0x1c2f5): undefined reference to `thermal_cooling_device_register'
acerhdf.c:(.init.text+0x1c360): undefined reference to `thermal_zone_device_register'
drivers/built-in.o: In function `acerhdf_unregister_thermal':
acerhdf.c:(.text.unlikely+0x3c67): undefined reference to `thermal_cooling_device_unregister'
acerhdf.c:(.text.unlikely+0x3c91): undefined reference to `thermal_zone_device_unregister'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Peter Feuerer <peter@piie.net>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>