util_libs: Add in symlink for nexus

This brings in the C stub used by shodan for the nexus platform. This is only necessary for
running sel4test in the nexus platform. Cantrip itself does not use libplatsupport, and these
functions are simply placeholders that return bogus values.

Change-Id: I7a96e24a0874f71665a57fe854741f5aab754b08
diff --git a/libplatsupport/src/plat/nexus b/libplatsupport/src/plat/nexus
new file mode 120000
index 0000000..859a8a2
--- /dev/null
+++ b/libplatsupport/src/plat/nexus
@@ -0,0 +1 @@
\ No newline at end of file