meta-facebook: harma: fixed ttyS3

root@harma:~# find / -iname *serial-getty\@ttyS3*
/sys/fs/cgroup/system.slice/system-serial\x2dgetty.slice/serial-getty@ttyS3.service
/run/systemd/units/invocation:serial-getty@ttyS3.service
/etc/systemd/system/getty.target.wants/serial-getty@ttyS3.service

Change-Id: If97e95efd32272a0b88dd39dd3b1f6116e6dc04e
Signed-off-by: Peter Yin <peter.yin@quantatw.com>
diff --git a/meta-facebook/meta-harma/conf/machine/harma.conf b/meta-facebook/meta-harma/conf/machine/harma.conf
index 7b205cc..3beb5e1 100644
--- a/meta-facebook/meta-harma/conf/machine/harma.conf
+++ b/meta-facebook/meta-harma/conf/machine/harma.conf
@@ -23,4 +23,5 @@
 VIRTUAL-RUNTIME_obmc-host-state-manager = "phosphor-state-manager-host"
 VIRTUAL-RUNTIME_obmc-chassis-state-manager = "phosphor-state-manager-chassis"
 
-SERIAL_CONSOLES += " 57600;ttyS3"
+# There is an additional serial console to the CMM (Minerva) on ttyS3.
+SERIAL_CONSOLES:append = " 57600;ttyS3"