docs(versal): add TSP build documentation

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

Change-Id: I7106ab477a881c58e1c45863bd6854d188982282
Signed-off-by: Prasad Kummari <prasad.kummari@amd.com>
diff --git a/docs/plat/xilinx-versal.rst b/docs/plat/xilinx-versal.rst
index 09a6ee2..b71776d 100644
--- a/docs/plat/xilinx-versal.rst
+++ b/docs/plat/xilinx-versal.rst
@@ -19,6 +19,11 @@
 make RESET_TO_BL31=1 CROSS_COMPILE=aarch64-none-elf- PLAT=versal VERSAL_PLATFORM=versal_virt bl31
 ```
 
+To build bl32 TSP you have to rebuild bl31 too
+```bash
+make CROSS_COMPILE=aarch64-none-elf- PLAT=versal 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 bl31 VERSAL_CONSOLE=dcc