clocksource/drivers/sun4i: Add the COMPILE_TEST option

Increase the compilation test coverage by adding the COMPILE_TEST option.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -71,8 +71,10 @@ config ORION_TIMER
 	  Enables the support for the Orion timer driver
 
 config SUN4I_TIMER
+	bool "Sun4i timer driver" if COMPILE_TEST
 	select CLKSRC_MMIO
-	bool
+	help
+	  Enables support for the Sun4i timer.
 
 config SUN5I_HSTIMER
 	select CLKSRC_MMIO