meta-facebook: rainier: Add back mctp file append

When building rainiera 6 and 7, we were getting errors saying
QA Issue: mctp: Files/directories were installed but not shipped in any package

Change-Id: I1aaebb89f3099bdfed652c8623918023be9035be
Signed-off-by: James Athappilly <jamesatha@gmail.com>

meta-facebook/meta-rainiera7/recipes-phosphor/mctp/mctp_%.bbappend

diff --git a/meta-facebook/meta-rainiera7/recipes-phosphor/mctp/mctp_%.bbappend b/meta-facebook/meta-rainiera7/recipes-phosphor/mctp/mctp_%.bbappend
index 6bbffe6..be490c9 100644
--- a/meta-facebook/meta-rainiera7/recipes-phosphor/mctp/mctp_%.bbappend
+++ b/meta-facebook/meta-rainiera7/recipes-phosphor/mctp/mctp_%.bbappend
@@ -20,6 +20,10 @@
     rainier-mctp-i3c@0.service \
 "
 
+FILES:${PN}:append = " \
+    ${systemd_system_unitdir}/rainier-mctp-i3c@.service \
+"
+
 RDEPENDS:${PN}:append = "bash"
 
 do_install:append () {