clocksource/drivers/tegra186: Put Kconfig option 'tristate' to 'bool'

The clocksources are built-in, they are not modules. We don't know if
the core time framework is ready for clockevents / clocksources as
modules.

Revert back this option to 'bool'.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20220718213657.1303538-1-daniel.lezcano@linaro.org

drivers/clocksource/Kconfig

@@ -158,7 +158,7 @@ config TEGRA_TIMER
 	  Enables support for the Tegra driver.
 
 config TEGRA186_TIMER
-	tristate "NVIDIA Tegra186 timer driver"
+	bool "NVIDIA Tegra186 timer driver"
 	depends on ARCH_TEGRA || COMPILE_TEST
 	depends on WATCHDOG && WATCHDOG_CORE
 	help