ARM: tegra: Guard clock code with a Kconfig symbol

Clock code is not relevant on all Tegra SoC generations, so guard it
with a Kconfig symbol that can be selected by the generations that need
it.

This is in preparation for unifying Tegra186 code with the code used on
older generations.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/arch/arm/mach-tegra/board.c b/arch/arm/mach-tegra/board.c
index 4e15907..209416e 100644
--- a/arch/arm/mach-tegra/board.c
+++ b/arch/arm/mach-tegra/board.c
@@ -9,7 +9,9 @@
 #include <ns16550.h>
 #include <spl.h>
 #include <asm/io.h>
+#if IS_ENABLED(CONFIG_TEGRA_CLKRST)
 #include <asm/arch/clock.h>
+#endif
 #include <asm/arch/funcmux.h>
 #include <asm/arch/mc.h>
 #include <asm/arch/tegra.h>