ARM: tegra: Use architected timer on ARMv8

ARMv8 requires an architected timer to be present, so it can be used
instead of the Tegra US timer. This allows for better code reuse.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

include/configs/tegra-common.h

@@ -18,8 +18,11 @@
 
 #include <asm/arch/tegra.h>		/* get chip and board defs */
 
+/* Use the Tegra US timer on ARMv7, but the architected timer on ARMv8. */
+#ifndef CONFIG_ARM64
 #define CONFIG_SYS_TIMER_RATE		1000000
 #define CONFIG_SYS_TIMER_COUNTER	NV_PA_TMRUS_BASE
+#endif
 
 /*
  * Display CPU and Board information