ci(n1sdp): add PSCI runtime instrumentation tests

Add fragments to enable building FIP images with TFTF on N1SDP. There's
no support for this at the moment. With this in place, add fragments and
a test configuration to enable the "Runtime Instrumentation" test suite
to be run.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: I43afb806777de6e128ebe9686708c78cce26673a
diff --git a/tftf_config/n1sdp-runtime-instrumentation b/tftf_config/n1sdp-runtime-instrumentation
new file mode 100644
index 0000000..8afbfe4
--- /dev/null
+++ b/tftf_config/n1sdp-runtime-instrumentation
@@ -0,0 +1,3 @@
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=n1sdp
+TESTS=runtime-instrumentation