scripts/checkpatch: Fix MAINTAINERS update warning with --terse

We recently improved the MAINTAINERS update warning to show the files
that trigger it.  Example:

    WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
    #105:
    deleted file mode 100644

improved to

    WARNING: added, moved or deleted file(s):

      migration/threadinfo.h
      migration/threadinfo.c

    Does MAINTAINERS need updating?

Unfortunately, this made things worse with --terse, as only the first
line of each warning is shown then.

    WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?

became

    WARNING: added, moved or deleted file(s):

Adjust the warning text to

    WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
      migration/threadinfo.h
      migration/threadinfo.c

so we get the exact same warning as we used to with --terse.

Fixes: 1d745e6d96 (scripts/checkpatch: use new hook for MAINTAINERS update check)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[DB: fix typo with missing string concat operator]
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/checkpatch.pl

@@ -1474,9 +1474,9 @@ sub process_file_list {
 
 	# If we don't see a MAINTAINERS update, prod the user to check
 	if (int(@maybemaintainers) > 0 && !$sawmaintainers) {
-		WARN("added, moved or deleted file(s):\n\n  " .
-		     join("\n  ", @maybemaintainers) .
-		     "\n\nDoes MAINTAINERS need updating?\n");
+                WARN("added, moved or deleted file(s),"
+		     . " does MAINTAINERS need updating?\n  "
+		     . join("\n  ", @maybemaintainers));
 	}
 }