regulators: Add/install base service

Create a service file to start the phosphor-regulators binary that will
be linked to the multi-user target so that its started at BMC standby.
Add this service file to be installed within the systemd services
directory(`/lib/systemd/system/`).

Change https://gerrit.openbmc-project.xyz/27972 installs the binary

Tested:
    Service file installed in /lib/systemd/system/
    Linked to multi-user target in recipe and it started at BMC standby

Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
Change-Id: I5ef1485569ada2737e0e8d5ce11965c4eff0eb45
diff --git a/meson.build b/meson.build
index e4e8aa2..9cfb46c 100644
--- a/meson.build
+++ b/meson.build
@@ -46,7 +46,8 @@
     'power-supply-monitor@.service',
     'pseq-monitor-pgood.service',
     'pseq-monitor.service',
-    'phosphor-psu-monitor.service'
+    'phosphor-psu-monitor.service',
+    'phosphor-regulators.service'
 ]
 
 foreach service : services