Doc: Removed TF-M prefix from document heading

This patch removes the TF-M/Trusted Firmware prefix from the
title heading across the documentation.

Change-Id: I60e0c6e48615f67ee040a0d6dbc7d6f1873856e7
Signed-off-by: Galanakis, Minos <minos.galanakis@arm.com>
19 files changed