clock: add Tegra186 clock driver

In Tegra186, on-SoC clocks are manipulated using IPC requests to the BPMP
(Boot and Power Management Processor). This change implements a driver
that does that. A tegra/ sub-directory is created to follow the existing
pattern. It is unconditionally selected by CONFIG_TEGRA186 since virtually
any Tegra186 build of U-Boot will need the feature.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index ec2d8ac..e8186d5 100644
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -64,9 +64,11 @@
 
 config TEGRA186
 	bool "Tegra186 family"
+	select CLK
 	select DM_MAILBOX
 	select MISC
 	select TEGRA186_BPMP
+	select TEGRA186_CLOCK
 	select TEGRA186_GPIO
 	select TEGRA_ARMV8_COMMON
 	select TEGRA_HSP