platform: Added deprecation warnings for AN539

This patch modifies the cmake configuration
for AN539 to display the deprecation warning at build-time.

It also adds a LOG_MESSAGE entry on the spm_hal which
displays a run-time notification.

The Deprecated Platforms section of the documentation is
updated to reflect this status change.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Change-Id: I1cddb70427ec314562197bca65aeb15172418c39
diff --git a/docs/contributing/platform_deprecation.rst b/docs/contributing/platform_deprecation.rst
index 29e2e83..71cda15 100644
--- a/docs/contributing/platform_deprecation.rst
+++ b/docs/contributing/platform_deprecation.rst
@@ -54,9 +54,9 @@
 |                              | after     |                                   |
 |                              | release   |                                   |
 +==============================+===========+===================================+
-|                              |           |                                   |
+|    mps2/an539                | 1.2       |   N.A                             |
 +------------------------------+-----------+-----------------------------------+
 
 --------------
 
-*Copyright (c) 2020, Arm Limited. All rights reserved.*
\ No newline at end of file
+*Copyright (c) 2020, Arm Limited. All rights reserved.*