clocksource/drivers/bcm2835: Add the COMPILE_TEST option

Change the Kconfig option logic to fullfil with the current approach.

A new Kconfig option is added, CONFIG_BCM2835_TIMER and is selected by the
platform. Then the clocksource's Kconfig is changed to make this option
selectable by the user if the COMPILE_TEST option is set. Otherwise, it
is up to the platform's Kconfig to select the timer.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

arch/arm/mach-bcm/Kconfig

@@ -143,6 +143,7 @@ config ARCH_BCM2835
 	select ARM_TIMER_SP804
 	select HAVE_ARM_ARCH_TIMER if ARCH_MULTI_V7
 	select CLKSRC_OF
+	select BCM2835_TIMER
 	select PINCTRL
 	select PINCTRL_BCM2835
 	help

drivers/clocksource/Kconfig

@@ -27,6 +27,13 @@ config CLKBLD_I8253
 config CLKSRC_MMIO
 	bool
 
+config BCM2835_TIMER
+	bool "BCM2835 timer driver" if COMPILE_TEST
+	depends on GENERIC_CLOCKEVENTS
+	select CLKSRC_MMIO
+	help
+	  Enables the support for the BCM2835 timer driver.
+
 config DIGICOLOR_TIMER
 	bool "Digicolor timer driver" if COMPILE_TEST
 	depends on GENERIC_CLOCKEVENTS

drivers/clocksource/Makefile

@@ -19,7 +19,7 @@ obj-$(CONFIG_CLKSRC_NOMADIK_MTU)	+= nomadik-mtu.o
 obj-$(CONFIG_CLKSRC_DBX500_PRCMU)	+= clksrc-dbx500-prcmu.o
 obj-$(CONFIG_ARMADA_370_XP_TIMER)	+= time-armada-370-xp.o
 obj-$(CONFIG_ORION_TIMER)	+= time-orion.o
-obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835_timer.o
+obj-$(CONFIG_BCM2835_TIMER)	+= bcm2835_timer.o
 obj-$(CONFIG_ARCH_CLPS711X)	+= clps711x-timer.o
 obj-$(CONFIG_ARCH_ATLAS7)	+= timer-atlas7.o
 obj-$(CONFIG_ARCH_MOXART)	+= moxart_timer.o