Add Sonic Login Manager SELinux rule to allow it to start SonicDE X11

sonic-login-manager-selinux/plasmalogin-selinux.te

@@ -0,0 +1,12 @@
+module plasmalogin-selinux 1.0;
+
+require {
+    type unconfined_t;
+    type xdm_exec_t;
+    class file { entrypoint execute };
+}
+
+# Allow the plasmalogin process to execute the X11 user helper binary
+# which is labeled as xdm_exec_t. This is needed when the plasmalogin
+# daemon is not running in the xdm_t domain on SELinux enforcing systems.
+allow unconfined_t xdm_exec_t:file { entrypoint execute };