Tegra: introduce delay timer support

This patch introduces the backend required for implementing the delay
timer API. Tegra has an on-chip free flowing us timer which can be
used as the delay timer.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
diff --git a/plat/nvidia/tegra/include/tegra_private.h b/plat/nvidia/tegra/include/tegra_private.h
index fa29fbb..d0cde2a 100644
--- a/plat/nvidia/tegra/include/tegra_private.h
+++ b/plat/nvidia/tegra/include/tegra_private.h
@@ -74,4 +74,7 @@
 plat_params_from_bl2_t *bl31_get_plat_params(void);
 int bl31_check_ns_address(uint64_t base, uint64_t size_in_bytes);
 
+/* Declarations for tegra_delay_timer.c */
+void tegra_delay_timer_init(void);
+
 #endif /* __TEGRA_PRIVATE_H__ */