meta-zaius: obmc-phosphor-image: add machine suffix

For obmc-phosphor-image, add zaius machine suffix to avoid poisoning other
machines using this layer.

Change-Id: I417b4b3bedf542cca7ea5d2b63752192160bb964
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/meta-zaius/recipes-phosphor/image/obmc-phosphor-image.bbappend b/meta-zaius/recipes-phosphor/image/obmc-phosphor-image.bbappend
index aa57bbf..7cff3bb 100644
--- a/meta-zaius/recipes-phosphor/image/obmc-phosphor-image.bbappend
+++ b/meta-zaius/recipes-phosphor/image/obmc-phosphor-image.bbappend
@@ -1 +1 @@
-OBMC_IMAGE_EXTRA_INSTALL_append = " mboxd"
+OBMC_IMAGE_EXTRA_INSTALL_append_zaius = " mboxd"