doc: Reformat platform port documents

The platform port documents are not very standardised right now and
they don't integrate properly into the document tree so:

1) Make sure each port has a proper name and title (incl. owner)
2) Correct use of headings, subheadings, etc in each port
3) Resolve any naming conflicts between documents

Change-Id: I4c2da6f57172b7f2af3512e766ae9ce3b840b50f
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/plat/index.rst b/docs/plat/index.rst
index 3a917f3..5951413 100644
--- a/docs/plat/index.rst
+++ b/docs/plat/index.rst
@@ -16,7 +16,6 @@
    meson-gxl
    mt8183
    nvidia-tegra
-   poplar
    qemu
    rcar-gen3
    rockchip
@@ -26,4 +25,5 @@
    synquacer
    ti-k3
    warp7
+   xilinx-versal
    xilinx-zynqmp