feat(versal-net): add jtag dcc support

Add support for JTAG Debug Communication Channel(DCC), using the dcc
console driver, for Versal NET platform.
UART0/UART1 is not configured when the JTAG DCC is used as console for
the platform.
Though DCC is not using any UART, VERSAL_NET_UART_BASE needs
to be defined in the platform code. If its not defined, build errors
are observed.
Now VERSAL_NET_UART_BASE by default points to UART0 base.
Check for valid console(pl011, pl011_0, pl011_1, dcc) is
being done in the platform makefile, the error condition in
setting the value of VERSAL_NET_UART_BASE is redundant, thus the error
message is removed from the code.

Change-Id: I1085433055abea13526230cff4d4183ff7a01477
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
diff --git a/docs/plat/xilinx-versal-net.rst b/docs/plat/xilinx-versal-net.rst
index 5d2e663..5d04639 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 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
+```
+
 Xilinx Versal NET platform specific build options
 -------------------------------------------------
 
@@ -23,8 +28,9 @@
 *   `VERSAL_NET_BL32_MEM_SIZE`: Specifies the size of the memory region of the bl32 binary.
 
 *   `VERSAL_NET_CONSOLE`: Select the console driver. Options:
-    -   `pl011`, `pl011_0`: ARM pl011 UART 0
+    -   `pl011`, `pl011_0`: ARM pl011 UART 0 (default)
     -   `pl011_1`         : ARM pl011 UART 1
+    -   `dcc`             : JTAG Debug Communication Channel(DCC)
 
 *   `TFA_NO_PM` : Platform Management support.
     -    0 : Enable Platform Management (Default)