Bluetooth: audio: has: Fix building with preset support disabled

This fixes regression causing compilation errors seen when the
code is built without preset support (BT_HAS_PRESET_COUNT = 0).

Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>

samples/bluetooth/hap_ha/sample.yaml

@@ -7,6 +7,13 @@ tests:
     platform_allow: native_posix
     tags: bluetooth
     build_only: true
+  sample.bluetooth.hap_ha.monaural_no_presets:
+    harness: bluetooth
+    platform_allow: native_posix
+    tags: bluetooth
+    build_only: true
+    extra_configs:
+      - CONFIG_BT_HAS_PRESET_COUNT=0
   sample.bluetooth.hap_ha.banded:
     harness: bluetooth
     platform_allow: native_posix

samples/bluetooth/hap_ha/src/has_server.c

@@ -96,5 +96,9 @@ int has_server_init(void)
 		return err;
 	}
 
-	return has_server_preset_init();
+	if (IS_ENABLED(CONFIG_BT_HAS_PRESET_SUPPORT)) {
+		return has_server_preset_init();
+	}
+
+	return 0;
 }