build: use allowed over enabled

Meson feature options are typically in a tri-state of enabled, disabled,
or auto.  The enabled and disabled functions on an option (from
`get_option`) no longer return true for auto features.  Instead, the
expectation is to use `allowed()` which is true for both enabled and auto.

Switch all uses of `enabled` to `allowed`.

Change-Id: I882edd53856df38c8292bc3313b9342b2b1ceddd
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/service_files/meson.build b/service_files/meson.build
index 5f5b78c..cfa3297 100644
--- a/service_files/meson.build
+++ b/service_files/meson.build
@@ -13,7 +13,7 @@
 ]
 
 foreach tuple : unit_files
-    if get_option(tuple[0]).enabled()
+    if get_option(tuple[0]).allowed()
         configure_file(
             copy: true,
             input: tuple[1],