To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/

Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

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>