ci: exclude rdn1edge and sgi575 source files for coverage

The build of the rdn1edge and sgi575 platforms has been removed as
part of this change 17331, resulting in coverage failures. Hence
added source files correspoding to these platforms into the exclusion
list.

Change-Id: If2b85a052634b0dd3104ea5f6534369a5a5c1e38
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
1 file changed