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: Ieb1a6b353443eabfdc157a80b0e998e35202820f
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/usb-ctrl/meson.build b/usb-ctrl/meson.build
index af207f4..c490229 100644
--- a/usb-ctrl/meson.build
+++ b/usb-ctrl/meson.build
@@ -1,4 +1,4 @@
-if get_option('usb-ctrl').enabled()
+if get_option('usb-ctrl').allowed()
     install_data(
         'usb-ctrl',
         install_mode: 'rwxr-xr-x',