qapi2texi: minor python code simplification

Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <20180305172951.2150-2-marcandre.lureau@redhat.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

scripts/qapi/doc.py

@@ -134,10 +134,9 @@ def texi_enum_value(value):
 def texi_member(member, suffix=''):
     """Format a table of members item for an object type member"""
     typ = member.type.doc_type()
-    return '@item @code{%s%s%s}%s%s\n' % (
-        member.name,
-        ': ' if typ else '',
-        typ if typ else '',
+    membertype = ': ' + typ if typ else ''
+    return '@item @code{%s%s}%s%s\n' % (
+        member.name, membertype,
         ' (optional)' if member.optional else '',
         suffix)