clocksource: Provide timekeeping for efm32 SoCs

An efm32 features 4 16-bit timers with a 10-bit prescaler. This driver
provides clocksource and clock event device using one timer instance
each.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 5e940f8..915a388 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -71,6 +71,14 @@
 	help
 	  Use the always on PRCMU Timer as sched_clock
 
+config CLKSRC_EFM32
+	bool "Clocksource for Energy Micro's EFM32 SoCs" if !ARCH_EFM32
+	depends on OF && ARM && (ARCH_EFM32 || COMPILE_TEST)
+	default ARCH_EFM32
+	help
+	  Support to use the timers of EFM32 SoCs as clock source and clock
+	  event device.
+
 config ARM_ARCH_TIMER
 	bool
 	select CLKSRC_OF if OF