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/drivers/clk/Makefile b/drivers/clk/Makefile
index 3cbdd54..463b1d6 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -10,5 +10,7 @@
 obj-$(CONFIG_SANDBOX) += clk_sandbox.o
 obj-$(CONFIG_SANDBOX) += clk_sandbox_test.o
 obj-$(CONFIG_MACH_PIC32) += clk_pic32.o
+
+obj-y += tegra/
 obj-$(CONFIG_CLK_UNIPHIER) += uniphier/
 obj-$(CONFIG_CLK_EXYNOS) += exynos/