format-patch: --numbered-files and --stdout aren't mutually exclusive

For example:

    git format-patch --numbered-files --stdout --attach HEAD~~

will create two messages with files 1 and 2 attached respectively.
Without --attach/--inline but with --stdout, --numbered-files option
can be simply ignored, because we are not creating any file ourselves.
Signed-off-by: NStephen Boyd <bebarino@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-format-patch.txt

@@ -96,7 +96,6 @@ include::diff-options.txt[]
 --numbered-files::
 	Output file names will be a simple number sequence
 	without the default first line of the commit appended.
-	Mutually exclusive with the --stdout option.
 
 -k::
 --keep-subject::

builtin-log.c

@@ -917,8 +917,6 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		die ("-n and -k are mutually exclusive.");
 	if (keep_subject && subject_prefix)
 		die ("--subject-prefix and -k are mutually exclusive.");
-	if (numbered_files && use_stdout)
-		die ("--numbered-files and --stdout are mutually exclusive.");
 
 	argc = setup_revisions(argc, argv, &rev, "HEAD");
 	if (argc > 1)