tc2: update RSS configs to align with the TF-M source code changes

* Removed external TF-M test repository as it will be cloned and built by TF-M build process
* Updated SCP and AP load addresses with respect to RSS ATU
* Changed platform name (arm/rss to arm/rss/tc) to align with source code change.
* Updated image offsets in the flash bundle with respect to the source code change

Signed-off-by: Tintu Thomas <tintu.thomas@arm.com>
Change-Id: I2a1f31fcb5a8a5f5c7e60ff9f20df2860ab2ad7c