phosphor-base.inc: add var for automatic YAML subdirs

Some packages have directory trees of YAML files arranged based on
canonical organization names.  See
phosphor-logging-yaml-providers.bbclass as an example.

Add a variable that can be appended to by a layer to limit the number
of 'bbappends' that are necessary in a layer to add their
layer-specific organizations to all the YAML processing recipes.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I826cb3cd5623f4c8e635502cd9b1020c9df8ecb5
diff --git a/conf/distro/include/phosphor-base.inc b/conf/distro/include/phosphor-base.inc
index 297b2d3..4da31b7 100644
--- a/conf/distro/include/phosphor-base.inc
+++ b/conf/distro/include/phosphor-base.inc
@@ -143,3 +143,9 @@
 LAYER_CONF_VERSION ?= "8"
 
 KERNEL_CLASSES_append = " obmc-phosphor-kernel-version"
+
+# Some packages have directory trees of YAML files arranged based on
+# canonical organization names.  'xyz/openbmc_project' should be used
+# everywhere in phosphor, but some layers may append this with their
+# own organization(s).
+OBMC_ORG_YAML_SUBDIRS += " xyz/openbmc_project"