yaml: move to subdirectory

A pending sdbusplus change (I38b69bc67b6a3d80cda1b508a76e106a50d8ab93)
is going to require YAML to be in a specific subdirectory and not in
the root.  Move here in prep for that change.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I79e42014bbc15f10e7e2baf4a88dc05c6f2da698
diff --git a/gen/regenerate-meson b/gen/regenerate-meson
index 56bc2c6..a39ad64 100755
--- a/gen/regenerate-meson
+++ b/gen/regenerate-meson
@@ -19,5 +19,5 @@
 
 $SDBUSPP_GEN_MESON \
     --command meson \
-    --directory "$REPO_ROOT" \
+    --directory "$REPO_ROOT/yaml" \
     --output "$REPO_ROOT/gen"