clocksource/drivers/timer-atmel-pit: Rework Kconfig option

Allow building the PIT driver when COMPILE_TEST is enabled. Also remove its
default value so it can be disabled.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -399,8 +399,11 @@ config ARMV7M_SYSTICK
 	  This options enables support for the ARMv7M system timer unit
 
 config ATMEL_PIT
+	bool "Atmel PIT support" if COMPILE_TEST
+	depends on HAS_IOMEM
 	select TIMER_OF if OF
-	def_bool SOC_AT91SAM9 || SOC_SAMA5
+	help
+	  Support for the Periodic Interval Timer found on Atmel SoCs.
 
 config ATMEL_ST
 	bool "Atmel ST timer support" if COMPILE_TEST