refactor: change all occurrences of RSS to RSE

The Runtime Security Subsytem (RSS) was renamed to Runtime Security
Engine (RSE). Change all occurrences of "RSS"/"rss" in the code and file
names to "RSE"/"rse".
The related changes in TF-A can be found under the "rss_rse_rename"
topic: https://review.trustedfirmware.org/q/topic:%22rss_rse_rename%22

Change-Id: Icd72ff3ed2d63e87d84baadfab02ccf75a545d08
Signed-off-by: David Vincze <david.vincze@arm.com>
14 files changed