docs(versal2): add AMD Versal Gen 2 documentation

Add information about AMD Versal Gen 2 platform for TF-A Tests and
the build commands.

Change-Id: If1ab592064a6ba39c87e62c32e6e74cd6026caec
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/docs/plat/index.rst b/docs/plat/index.rst
index 33c0ab9..b0ebc46 100644
--- a/docs/plat/index.rst
+++ b/docs/plat/index.rst
@@ -6,6 +6,7 @@
    :caption: Contents
    :hidden:
 
+   xilinx-versal2
    xilinx-versal_net
    xilinx-versal
    xilinx-zynqmp