Doc: Add changelog for 1.1 release

Create changelog document for 1.1 release and add it to the main
changelog document.
Add 1.1 release to readme.rst
Update version number in tfm_version.h
Update version number in Doxygen CMake files.

Change-Id: Icb81ab1e5994228772884c7a1dcb878533dcfa33
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
6 files changed