ci: Use SCP/MCP v2.8.0-dev release binaries for CSS platforms

This patch makes use of SCP/MCP v2.8.0-dev release binaries
for the following FVP CSS platforms:
- rdn1edge
- rdn1edgex2
- sgi575
- sgm775
- tc0

Once the SCP-firmware has released v2.8 version, the binaries
and path will be updated accordingly.

Change-Id: I442523e1bb5d7650d5886d1f588dfb9ba22766f6
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
6 files changed