clocksource: Select CLKSRC_MMIO where needed

The Tegra clocksource implementation uses the clocksource_mmio helper
functions, but currently can be configured without them, which fails:

drivers/clocksource/built-in.o: In function `tegra20_init_timer':
:(.init.text+0xac): undefined reference to `clocksource_mmio_init'
:(.init.text+0x140): undefined reference to `clocksource_mmio_readl_up'

The same problem exists for Digicolor:

drivers/clocksource/built-in.o: In function `digicolor_timer_init':
:(.init.text+0xfa): undefined reference to `clocksource_mmio_init'
:(.init.text+0x14c): undefined reference to `clocksource_mmio_readl_down'

I've inspected the Kconfig file to look for other cases that I have not
yet run into, and added an explicit 'select' to each one to ensure we
can successfully link the drivers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: http://lkml.kernel.org/r/1453737776-1960372-1-git-send-email-arnd@arndb.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/clocksource/Kconfig

@@ -30,6 +30,7 @@ config CLKSRC_MMIO
 config DIGICOLOR_TIMER
 	bool "Digicolor timer driver" if COMPILE_TEST
 	depends on GENERIC_CLOCKEVENTS
+	select CLKSRC_MMIO
 	help
 	  Enables the support for the digicolor timer driver.
 
@@ -55,6 +56,7 @@ config ARMADA_370_XP_TIMER
 	bool "Armada 370 and XP timer driver" if COMPILE_TEST
 	depends on ARM
 	select CLKSRC_OF
+	select CLKSRC_MMIO
 	help
 	  Enables the support for the Armada 370 and XP timer driver.
 
@@ -89,6 +91,7 @@ config SUN5I_HSTIMER
 
 config TEGRA_TIMER
 	bool "Tegra timer driver" if COMPILE_TEST
+	select CLKSRC_MMIO
 	depends on ARM
 	help
 	  Enables support for the Tegra driver.
@@ -263,6 +266,7 @@ config FSL_FTM_TIMER
 
 config VF_PIT_TIMER
 	bool
+	select CLKSRC_MMIO
 	help
 	  Support for Period Interrupt Timer on Freescale Vybrid Family SoCs.
 
@@ -394,6 +398,7 @@ config CLKSRC_ST_LPC
 	bool "Low power clocksource found in the LPC" if COMPILE_TEST
 	select CLKSRC_OF if OF
 	depends on HAS_IOMEM
+	select CLKSRC_MMIO
 	help
 	  Enable this option to use the Low Power controller timer
 	  as clocksource.