refactor(sgi): change "sgi" to "nrd" within file names

As part of the move from "sgi" to "neoverse_rd", rename every occurance
of "sgi" within file names to "nrd".

Signed-off-by: Rohit Mathew <Rohit.Mathew@arm.com>
Change-Id: I587072f1dd42bbda2730e24139c88945908aa730
24 files changed