acerhdf: Use bang-bang thermal governor

acerhdf has been doing an on-off fan control using hysteresis by
post-manipulating the outcome of thermal subsystem trip point handling.
This patch enables acerhdf to use the bang-bang governor, which is
intended for on-off controlled fans.

Cc: platform-driver-x86@vger.kernel.org
Cc: Darren Hart <dvhart@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
CC: Zhang Rui <rui.zhang@intel.com>
Cc: Andreas Mohr <andi@lisas.de>
Cc: Javi Merino <javi.merino@arm.com>
Acked-and-tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Peter Feuerer <peter@piie.net>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 854cc50..ba77611 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -38,7 +38,8 @@
 
 config ACERHDF
 	tristate "Acer Aspire One temperature and fan driver"
-	depends on THERMAL && ACPI
+	select THERMAL_GOV_BANG_BANG
+	depends on ACPI
 	---help---
 	  This is a driver for Acer Aspire One netbooks. It allows to access
 	  the temperature sensor and to control the fan.