refactor(sgi): replace all references to "sgi" within scripts

Currently, some of the platform utility scripts use "sgi" as a prefix to
name certain variables. As these platforms have moved away from "sgi",
update the prefix to "nrd" for the same.

Signed-off-by: Rohit Mathew <Rohit.Mathew@arm.com>
Change-Id: I0fa094e6d6fb08972b3c7d246b3b9341b50fa2ab
diff --git a/rdv1_utils.sh b/rdv1_utils.sh
index a0d0a2d..6486a42 100644
--- a/rdv1_utils.sh
+++ b/rdv1_utils.sh
@@ -13,8 +13,8 @@
 scp_mcp_prebuilts="${scp_mcp_prebuilts:-$scp_mcp_downloads/rdv1/release}"
 
 
-kernel_list[sgi-busybox]="$nrd_prebuilts/Image"
-initrd_list[sgi-ramdisk]="$nrd_prebuilts/ramdisk-busybox.img"
+kernel_list[nrd-busybox]="$nrd_prebuilts/Image"
+initrd_list[nrd-ramdisk]="$nrd_prebuilts/ramdisk-busybox.img"
 
 scp_ram_addr=0x0bd80000
 mcp_ram_addr=0x0BF80000