regs: Add/install monitor enable service

Create a service file to call a method within the phosphor-regulators
binary to enable monitoring of the regulators. Add this service file to
be installed within the systemd services
directory(`/lib/systemd/system/`).

Tested:
    Monitoring is enabled after power on is complete
    Enablement of monitor does not block any other services

Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
Change-Id: Ieee747c00ef748140511a50324201c11d9c8738f
diff --git a/meson.build b/meson.build
index 6a1dc6d..9e8adb4 100644
--- a/meson.build
+++ b/meson.build
@@ -49,7 +49,8 @@
     'pseq-monitor.service',
     'phosphor-psu-monitor.service',
     'phosphor-regulators.service',
-    'phosphor-regulators-config.service'
+    'phosphor-regulators-config.service',
+    'phosphor-regulators-monitor-enable.service'
 ]
 
 foreach service : services