docs: pci: endpoint/function/binding/pci-test.txt convert to ReST

Convert this file to ReST by adding a proper title to it and
use the right markups for a table.

While here, add a SPDX header.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6254963b85417e44865dab05e4b99cd485074132.1592203650.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>