clocksource/drivers/samsung-pwm: 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

@@ -237,7 +237,7 @@ config CLKSRC_EXYNOS_MCT
 	  Support for Multi Core Timer controller on Exynos SoCs.
 
 config CLKSRC_SAMSUNG_PWM
-	bool
+	bool "PWM timer drvier for Samsung S3C, S5P" if COMPILE_TEST
 	help
 	  This is a new clocksource driver for the PWM timer found in
 	  Samsung S3C, S5P and Exynos SoCs, replacing an earlier driver