docs: pci: boot-interrupts.rst: improve html output

docs: pci: boot-interrupts.rst: improve html output

There are some warnings with this file:

    /Documentation/PCI/boot-interrupts.rst:42: WARNING: Unexpected indentation.
    /Documentation/PCI/boot-interrupts.rst:52: WARNING: Block quote ends without a blank line; unexpected unindent.
    /Documentation/PCI/boot-interrupts.rst:92: WARNING: Unexpected indentation.
    /Documentation/PCI/boot-interrupts.rst:98: WARNING: Unexpected indentation.
    /Documentation/PCI/boot-interrupts.rst:136: WARNING: Unexpected indentation.

It turns that this file conversion to ReST could be improved,
in order to remove the warnings and provide a better output.

So, fix the warnings by adjusting blank lines, add a table and
some list markups. Also, mark endnodes as such.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/a6a9eb16eede10731bcce69a600ab12d92e6ba47.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>