Build: Enable PS NV counter test by default

This patch enables the PS NV counter tests by default.
But there is no effect of it when regression tests are disabled.

Documentation of it is updated as well.

Change-Id: Ibbce9da66f0242135ba71f8b8e9f0225823ca66f
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
3 files changed