meson: switch code dependency to libsystemd

For a while now systemd has packaged a separate `libsystemd`.  For
meson dependency, `systemd` should be used when looking for systemd
service file paths and `libsystemd` should be used for `sd_*` functions.

Update the dependency accordingly.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9768dd66c4180085f201a0b77385d696bdd1680f
diff --git a/user_channel/meson.build b/user_channel/meson.build
index d4f1126..a18ed06 100644
--- a/user_channel/meson.build
+++ b/user_channel/meson.build
@@ -5,10 +5,10 @@
   dependencies: [
     crypto,
     ipmid_dep,
+    libsystemd_dep,
     nlohmann_json_dep,
     phosphor_dbus_interfaces_dep,
     phosphor_logging_dep,
-    systemd,
   ])
 
 channellayer_src = [
@@ -44,11 +44,11 @@
       channellayer_dep,
       crypto,
       ipmid_dep,
+      libsystemd_dep,
       nlohmann_json_dep,
       pam,
       phosphor_dbus_interfaces_dep,
       phosphor_logging_dep,
-      systemd,
     ])
 
   userlayer_src = [