powercap/drivers/dtpm: Add the experimental label to the option description

The DTPM framework will evolve in the next cycles. Let's add a
temporary EXPERIMENTAL tag to the option so users will be aware
the API may change over time.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/powercap/Kconfig

@@ -45,7 +45,7 @@ config IDLE_INJECT
 	  on a per CPU basis.
 
 config DTPM
-	bool "Power capping for Dynamic Thermal Power Management"
+	bool "Power capping for Dynamic Thermal Power Management (EXPERIMENTAL)"
 	help
 	  This enables support for the power capping for the dynamic
 	  thermal power management userspace engine.