Install example psu-update@.service

The repo needs an example psu-update@.service, it was expected to be
installed by a bitbake recipe, but during the recipe review it turns
out that the repo is better to install a default one and it could be
overriden by a bbappend.

Move the psu-update@.service from vendor-example to services directory
and install it.

Tested: Verify the service is installed.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I105b201972b32ca3d9e14878b92c9d038a41cbdb
diff --git a/meson.build b/meson.build
index 10748e5..bec51a2 100644
--- a/meson.build
+++ b/meson.build
@@ -9,11 +9,7 @@
 
 systemd = dependency('systemd')
 servicedir = systemd.get_pkgconfig_variable('systemdsystemunitdir')
-
-configure_file(input: 'service/xyz.openbmc_project.Software.Psu.Updater.service',
-               output: 'xyz.openbmc_project.Software.Psu.Updater.service',
-               copy: true,
-               install_dir: servicedir)
+subdir('services')
 
 # Common configurations for src and test
 cdata = configuration_data()