vhost-user: use an enum helper for features mask

The VHOST_USER_PROTOCOL_FEATURE_MASK will be automatically updated when
adding new features to the enum.

Signed-off-by: Thibaut Collet <thibaut.collet@6wind.com>
[Adapted from mailing list discussion - Marc-André]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Thibaut Collet <thibaut.collet@6wind.com>
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index d804c5f..78442ba 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -28,10 +28,15 @@
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
-#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x7ULL
-#define VHOST_USER_PROTOCOL_F_MQ         0
-#define VHOST_USER_PROTOCOL_F_LOG_SHMFD  1
-#define VHOST_USER_PROTOCOL_F_RARP       2
+enum VhostUserProtocolFeature {
+    VHOST_USER_PROTOCOL_F_MQ = 0,
+    VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
+    VHOST_USER_PROTOCOL_F_RARP = 2,
+
+    VHOST_USER_PROTOCOL_F_MAX
+};
+
+#define VHOST_USER_PROTOCOL_FEATURE_MASK ((1 << VHOST_USER_PROTOCOL_F_MAX) - 1)
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,