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: I2253ebff36b49c4b79b803175dd76668f8ac2ba8
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/util/meson.build b/util/meson.build
index 4b107d8..3797e5c 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -18,7 +18,7 @@
     phosphor_logging_dep,
 ]
 
-if get_option('phal').enabled()
+if get_option('phal').allowed()
     util_deps += dependency('libdt-api')
 endif