clocksource: Build Tegra timer on 32-bit ARM only

Instead of directly using the ARCH_TEGRA Kconfig symbol to enable this
driver, add a new, non-user-visible Kconfig symbol (TEGRA_TIMER) which
can be selected by the various SoCs.

This is useful to disable building the driver on Tegra132 (64-bit ARM)
where it doesn't currently compile but also isn't needed (yet).
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/mach-tegra/Kconfig

@@ -27,6 +27,7 @@ config ARCH_TEGRA_2x_SOC
 	select PINCTRL_TEGRA20
 	select PL310_ERRATA_727915 if CACHE_L2X0
 	select PL310_ERRATA_769419 if CACHE_L2X0
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra AP20 and T20 processors, based on the
 	  ARM CortexA9MP CPU and the ARM PL310 L2 cache controller
@@ -37,6 +38,7 @@ config ARCH_TEGRA_3x_SOC
 	select ARM_ERRATA_764369 if SMP
 	select PINCTRL_TEGRA30
 	select PL310_ERRATA_769419 if CACHE_L2X0
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T30 processor family, based on the
 	  ARM CortexA9MP CPU and the ARM PL310 L2 cache controller
@@ -47,6 +49,7 @@ config ARCH_TEGRA_114_SOC
 	select ARM_L1_CACHE_SHIFT_6
 	select HAVE_ARM_ARCH_TIMER
 	select PINCTRL_TEGRA114
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T114 processor family, based on the
 	  ARM CortexA15MP CPU
@@ -56,6 +59,7 @@ config ARCH_TEGRA_124_SOC
 	select ARM_L1_CACHE_SHIFT_6
 	select HAVE_ARM_ARCH_TIMER
 	select PINCTRL_TEGRA124
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T124 processor family, based on the
 	  ARM CortexA15MP CPU

drivers/clocksource/Kconfig

@@ -47,6 +47,9 @@ config SUN5I_HSTIMER
 	select CLKSRC_MMIO
 	bool
 
+config TEGRA_TIMER
+	bool
+
 config VT8500_TIMER
 	bool
 

drivers/clocksource/Makefile

@@ -27,7 +27,7 @@ obj-$(CONFIG_ARCH_U300)		+= timer-u300.o
 obj-$(CONFIG_SUN4I_TIMER)	+= sun4i_timer.o
 obj-$(CONFIG_SUN5I_HSTIMER)	+= timer-sun5i.o
 obj-$(CONFIG_MESON6_TIMER)	+= meson6_timer.o
-obj-$(CONFIG_ARCH_TEGRA)	+= tegra20_timer.o
+obj-$(CONFIG_TEGRA_TIMER)	+= tegra20_timer.o
 obj-$(CONFIG_VT8500_TIMER)	+= vt8500_timer.o
 obj-$(CONFIG_ARCH_NSPIRE)	+= zevio-timer.o
 obj-$(CONFIG_ARCH_BCM_MOBILE)	+= bcm_kona_timer.o