docs(versal-net): add TSP build documentation

Add information about Versal NET platform for TSP and provide
the build commands.

Change-Id: Id7c9d75f8a42813ca2bfd18494bfc6b73df0af52
Signed-off-by: Prasad Kummari <prasad.kummari@amd.com>
diff --git a/docs/plat/xilinx-versal-net.rst b/docs/plat/xilinx-versal-net.rst
index 5d04639..1db7695 100644
--- a/docs/plat/xilinx-versal-net.rst
+++ b/docs/plat/xilinx-versal-net.rst
@@ -14,6 +14,11 @@
 make RESET_TO_BL31=1 CROSS_COMPILE=aarch64-none-elf- PLAT=versal_net bl31
 ```
 
+To build bl32 TSP you have to rebuild bl31 too
+```bash
+make CROSS_COMPILE=aarch64-none-elf- PLAT=versal_net SPD=tspd RESET_TO_BL31=1 bl31 bl32
+```
+
 To build TF-A for JTAG DCC console:
 ```bash
 make RESET_TO_BL31=1 CROSS_COMPILE=aarch64-none-elf- PLAT=versal_net VERSAL_NET_CONSOLE=dcc bl31