filesystem: mount rw and overlay

Append base-files to add new fstab and depend on mount-overlay recipe.
Add systemd services to help mounting overlay fs.

Resolves openbmc/openbmc#2134

Change-Id: Ib56fcdde9f7364fca56a08e1ce72e7cafaac35b0
Signed-off-by: Edward A. James <eajames@us.ibm.com>
diff --git a/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend b/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend
new file mode 100644
index 0000000..d7e7a3b
--- /dev/null
+++ b/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend
@@ -0,0 +1,5 @@
+inherit obmc-phosphor-utils
+
+FILESEXTRAPATHS_prepend := "${@mf_enabled(d, 'obmc-ubi-fs', '${THISDIR}/${PN}:')}"
+
+RDEPENDS_${PN}_append += "${@mf_enabled(d, 'obmc-ubi-fs', 'mount-overlay-help')}"