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>

ARM platforms have migrated to the translation tables library v2.
However, for testing purposes, it can be useful to temporarily switch
back to the old version.

This patch introduces the option `ARM_XLAT_TABLES_LIB_V1`, that switches
to v1 of the library when is set to 1. By default, it is 0, so that ARM
platforms use the new version unless specifically stated.

Updated User Guide.

Change-Id: I53d3c8dd97706f6af9c6fca0364a88ef341efd31
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>