TF-A: Add build and coverity config for RD-N2 platform

Add build configuration for SPMC AT EL3 and SP at SEL0 on RD-N2
platform to tf-l1-build-fvp build group and include it in coverity
makefile.

Change-Id: Ia66de33f7f1ffba2b9248a8db7700c7fe54d0cd6
Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>
3 files changed