configs/rde1edge: allow support for RAS to be optional

In order to support build of RD-E1-Edge platform with and without
RAS support, add new build defintions ARM_TF_ENABLE_SPM and
ARM_TF_RAS_EXTENSION. These have to be set to '1' in order to
support SPM and RAS support.

Change-Id: Ia3629bf2236cc815ffe3b1e35b27b07e62cabf9d
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>