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/common/tegra_common.mk b/plat/nvidia/tegra/common/tegra_common.mk
index 5ec52fb..b88742a 100644
--- a/plat/nvidia/tegra/common/tegra_common.mk
+++ b/plat/nvidia/tegra/common/tegra_common.mk
@@ -48,6 +48,7 @@
 BL31_SOURCES		+=	drivers/arm/gic/gic_v2.c			\
 				drivers/arm/gic/gic_v3.c			\
 				drivers/console/console.S			\
+				drivers/delay_timer/delay_timer.c		\
 				drivers/ti/uart/16550_console.S			\
 				lib/cpus/aarch64/cortex_a53.S			\
 				lib/cpus/aarch64/cortex_a57.S			\
@@ -57,6 +58,7 @@
 				${COMMON_DIR}/drivers/pmc/pmc.c			\
 				${COMMON_DIR}/drivers/flowctrl/flowctrl.c	\
 				${COMMON_DIR}/tegra_bl31_setup.c		\
+				${COMMON_DIR}/tegra_delay_timer.c		\
 				${COMMON_DIR}/tegra_gic.c			\
 				${COMMON_DIR}/tegra_pm.c			\
 				${COMMON_DIR}/tegra_sip_calls.c			\