cantrip-os-rootserver: fill from sec on nexus platform

Change-Id: I3ee12b84dad2866028f95bc818a1172d1c73f9e4

cantrip-os-rootserver/Cargo.toml

diff --git a/cantrip-os-rootserver/Cargo.toml b/cantrip-os-rootserver/Cargo.toml
index e041c65..6e7f023 100644
--- a/cantrip-os-rootserver/Cargo.toml
+++ b/cantrip-os-rootserver/Cargo.toml
@@ -35,7 +35,7 @@
 ]
 CONFIG_PLAT_BCM2837 = ["fill_from_cpio"]
 CONFIG_PLAT_SHODAN = ["fill_from_cpio"]
-CONFIG_PLAT_NEXUS = ["fill_from_cpio"]
+CONFIG_PLAT_NEXUS = ["fill_from_sec"]
 # Used by sel4-config to extract kernel config
 CONFIG_PRINTING = []
 CONFIG_DEBUG_BUILD = []