clocksource/drivers/lpc32xx: 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>
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index a658190..ed7a824 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -146,9 +146,11 @@
 	  event device.
 
 config CLKSRC_LPC32XX
-	bool
+	bool "Clocksource for LPC32XX" if COMPILE_TEST
 	select CLKSRC_MMIO
 	select CLKSRC_OF
+	help
+	  Support for the LPC32XX clocksource.
 
 config CLKSRC_PISTACHIO
 	bool "Clocksource for Pistachio SoC" if COMPILE_TEST