Version: Update for TF-M v1.2.0 release

This patch updates the TF-M version for runtime code,
build system and documentation to v1.2.0

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Change-Id: I53b1e916a9928bac7347381d1a37c7d62bd2302a
diff --git a/docs/introduction/readme.rst b/docs/introduction/readme.rst
index b53c12c..914ea6d 100644
--- a/docs/introduction/readme.rst
+++ b/docs/introduction/readme.rst
@@ -186,6 +186,8 @@
 | v1.0        | 2020-03-27   | 1.0 release        | v20.03_API1.0     |
 +-------------+--------------+--------------------+-------------------+
 | v1.1        | 2020-07-15   | 1.1 release        | 1f960947          |
++---------------------------------------------------------------------+
+| v1.2.0      | 2020-11-25   | 1.2.0 release      | 90c8e680          |
 +-------------+--------------+--------------------+-------------------+
 
 Please refer to